Welcome Hopalong,
I think many of us here have spent a lifetime being lonely because of the relationships with either n parents or partners or both. Life with them is just as lonely as life without them, IMO.
Finding a partner who is not personality disordered when that is all you've known, is hard. It sounds like you have spent a lot of time on yourself--which is certainly key to not making those mistakes again. I think it is important to determine those characteristics that are most important to you before you start to date again, i.e., (since I don't know how old you are) does he want to have a family, or if one already exists, what kind of relationship does he have with his children and ex; if religion is important to you, is it also important to him; career aspirations for the both of you, etc., etc. Whatever it is that you feel must be present in someone with whom you want to be long term. Then I think that just observing his treatment of those who are close and familiar to him (including you, of course), and those who are strangers providing services (waitresses, etc.), can be a good starting point to learning his true character.
Taking it slow is important and anyone who wants to rush into a close relationship, is sending up a major red flag. The other important thing for me was to promise myself up front that if I saw a major red flag in someone I was dating, that I would immediately choose to terminate the relationship and move on rather than believe that it was something I could fix or change given enough time. That is not going to happen and it will eventually be the demise of the relationship.
I don't know if any of that was helpful to you, but it was how I approached the whole reentry into dating and has provided good results thus far. Good luck on your journey.
Brigid