Well, Boat... I don't have any pat answers for you or even lofty, vague, complex attempts to explain. I'm getting kinda foggy; thinking too much and working too much... and not having much fun doing either one of them, right now. I'm possessed with the Christmas deadline -- the one in my head.
If you're just hanging out, the guy is charming and fun... I don't see any harm in continuing to do so, even if you decide to put some limits on it. Some basic boundary of "I gotta go this other thing now, see ya soon" is good. Take a day or two for yourself to walk... get over the flu... pamper yourself, as best you can and let your feelings settle. He's not something you "have to do" or make decisions about in any particular way or timeline. Sometimes, it's good for oneself to "just go with the flow"... without expecting anything and just wait to see what does or doesn't happen. I'm a sucker for charming! Sometimes that's worked out really well; other times not. What I like about flirting with charming guys, is that it kind of opens up that part of me... creaky, rusty, stuck parts that haven't really grown or developed much... but I like the way I feel, trying to rise to the challenge and "play".
The other questions are harder and maybe just a tad beyond the specifics of one guy, one experience with guys. And I can't claim any particular expertise here... just my own experience and way of relating to people. I expect that everyone might answer those questions and think about them, differently... and all of those viewpoints could be considered "correct".
In reverse order, at the flirting stage I wouldn't exactly consider myself "involved" with the guy. So, like a competition (and again, I think this is just my style of relating) we are each responsible for protecting our own feelings behind our boundaries of self. Not expecting specific things... feeling cool with some of the unexpected things... asking about things that I don't understand, make me wary, or one way or another gives my intuition clues that I'm being challenged to move to another level... without being actually being asked in words, therefore not having the opportunity to decline gracefully. Much less ask myself if I want to, you know?
Example: hubs and I danced around each other a lot... neither of us making the first move. Finally, I had to ask him, what he was asking me... and when he said he didn't want to be pushy or selfish or possessive... I had to tell him: I don't go where I'm not invited. He laughed... and I got invited. That gave me the chance to say yes/no... and yeah, it's a bit on the formal negotiation side... but we were both wary, had been hurt or were currently hurting over relationships gone south... and we both had quite a bit at stake - emotionally, professionally, and life basics wise.
The thing about protecting people we're involved with... this is bigger than flirting. It's something I learned was part of how I was co-dependent; how I was always allowing myself to "take the bait" in the N-games in my FOO. I've seen the topic addressed alongside enabling alcoholics, too. Maybe it doesn't apply in this situation for you. But, when we try to protect other people's feelings... it can be like a subtle form of trying to control their feelings... by twisting ourselves into something we're not -- a lot of times; not necessarily always. One example would be, if you knew for a fact that you wouldn't be more than friends with this guy... but to avoid hurting his feelings (because you think he is starting to expect that the relationship will grow deeper; without knowing for sure) you continue to walk the tightrope of feeding his expectation... despite the fact that this now puts you in a tougher situation than just telling him you only want to be friends. There's mind-reading involved in this; and that weird form of "protecting someone's feelings" too. My understanding (limited as it is) is, that it's OVER-responsible to go to these lengths and is a form boundary transgression in itself. It's for sure, not what I personally consider honest anymore.
But, in a bigger sense even than that - you're right about the responsibility to protect people we're committed to. It's one of the fundamental emotional/physical commitments of the parent-child relationship. A child isn't physically able to protect itself and is dependent on the parent to do so. We protect our friends' too - being supportive, loyal, cheering them up or consoling them. And in these more romantic type relationships... protection comes later on, with trust, honesty, respect for boundaries and values and self & other, deeper caring, openness. One reason for me even starting this topic, is the fact that I've got some emotional confusion over this very thing.
And I guess, the source of that confusion is my Nmom's lack of protection of me - in fact, she herself violated my Self's "safety" and kept me on pins & needles, walking on eggshells. And of course, that's highly linked - associated in my brain patterns - with "love" and intimacy. Experience and repetition of experience has created an instinctual expectation for me, that if I open myself up to that degree with someone else... the same damned old bad things will happen. Deep down, there's this lesson that "Love" = "Doormat" = "not surviving". That's wrong; I know it's wrong intellectually, rationally. Emotionally, I'm still learning the "other" reality... still trying to undo the damage. And I'm slow as molasses in the artic about it. I feel fragile, vulnerable, confused and embarassed at my own lack of knowledge of what this "Love" and "like" thing really is. I have days when I'm just as skittish as a feral cat or even as dangerous as an abused dog. Really, those are good analogies.
So, we're up to, "what is like any ways"? That one woke my Twiggy up!

She pondered this way back when... and still doesn't really know what words make up the answer, scientifically. But, there is a real "chemistry" aspect to it among people. Just bio-stuff... and then there's personality. Some people just "click" together in a complimentary way - each distinctly different but fitting together. Hubs and I are like* this, in a lot of ways. In some other ways, we're too much alike -

-- and in other ways, we're total opposites, thankfully! Sometimes, people like what mirrors back a bit of themselves. That's how I explain people who always vote the same party ticket, in elections regardless of who's running. Sometimes, people like what's exotic, new and different from themselves. [ * hmmm - one meaning of like is "similar" ] I like my hubs because he's much fun; he's very affectionate (despite all my issues and over-thinking), he's always "been there" for me, even if he's not sure what I need... he'll ask! and he can do math in his head faster than people can use can calculators, sometimes. I like how he's always there to protect me, defend me, stand with me back to back to tackle any threat, challenge, or danger. I like how he doesn't make fun of me... when I'm anxious, panicky, freaked out by FOO-games.
But I love my hubs... just because I do. The totality of him and my experience of him causes this feeling in me. Because of who he is -- not all those things I like about him. I love him, even when I'm complaining about some of the things he does/doesn't do that irritate the hell out of me. I love him when I have to protect and defend him, too. Several of my friends warned me against him; predicted awful things... but after 10 years they haven't happened. He is who he says he is... there weren't any tricks... but not even that is enough explanation for the feeling. It's a mystery - always has been, my guess is it always will be. It's not subject to explanation because it's a thing that's alive somehow. Maybe at the atomic level or something...
and if I get addicted to it, well... it doesn't sound like a bad way to go!! I probably already am addicted to it, simply because of the deficit in my experience. We were invited to a Christmas party over the weekend, for example. It was a small company we used to do some work on the house. There was a great, pickup band; kids and dogs underfoot; food and people - very few of which we knew... and yet, I felt so welcome, so comfortable I really didn't want to go home!! It was absolutely nothing fancy and yet everyone had put caring and attention and FUN into it, pulled it together spontaneously... and in comparison to our neighborhood's social events... that kind of atmosphere and feeling is a lot more rare. I plan on doing something about that... because I think those people need it... and I know for sure, I do.
OK - that was my batch of rambling, from this pathetic brain. I think you'll figure it out Boat - or make it up as you go along - the ultimate creative project, right?
ps - I like you. You ask the bestest questions and make me think things I haven't thought about for a while or in just that way... I need the exercise! LOL...