H&H - it sounds to me as though you were standing up for yourself, and wrapping up some 'unfinished business'.
As far as its being 'stupid', as you put it in your title, I'm not so sure of that.
When dealing with abusers, we have a very limited range of choices. 'Work out a decent relationship and end up on peaceful, equal terms' is not usually on the list of options, unless the person who is abusing us is simply emotionally tone-deaf, rather than truly abusive. Instead, the menu selections are more like this:
-be maligned and bear it silently as long as you can; you will blow up or act out in some other way periodically, because no human being can absorb abuse infinitely without showing the effects
-break off contact so that you aren't there to witness being maligned; you will still be maligned, and you will still be bearing it silently because you are not there to defend yourself, but you won't know what's being said and you won't experience the abuse directly. You may still get it indirectly through the third parties who believe what's being said about you, though, and you need to decide how you'll deal with that, sooner or later.
-set the record straight, directly and in public, if you can; understand, however, that you are doing this only for yourself, for your own emotional health, because you can't make your abuser honest any more than you can make him non-abusive. You may be able to 'get through' to some of his followers, but don't make that your goal, because you will inevitably be disappointed -- many people prefer to believe malicious fabrications because of the drama dependency problem [life's more interesting when it resembles soap opera]. [Since abusers 'hate to lose', you're likely to have further malice to contend with, but if you stand firm, they'll soon look for safer targets elsewhere.]
-set the record straight in a safe, private setting [such as with a therapist]; again, this is for your own emotional health primarily. [This has the advantage that you don't get as much direct retaliation from the abuser, but the disadvantage that you still have the abuse going on just as before; sometimes increased awareness makes it easier to tolerate abuse, but sometimes it makes it much more difficult to put up with!]
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In your case, I suspect that being an expectant mother has brought out some strong protective impulses.
You don't want this man having anything to do with your child, perhaps? Might that be why you are taking a strong stand now?
The dream about your husband - the nightmare, I should say - might just be your subconscious telling you in very dramatic terms that protection of your family from your biological father is going to be up to you, not something your husband can do for you; you're the one who has to stand firm and lock the door - if that is where you are headed. At the gentlest extreme, it's still you who has to stand firm and define the boundaries.
The dream might also be warning you about things that threaten your family harmony - and an openly slanderous N parent can certainly be a threat to a family's harmony.
Just a few thoughts. They may be helpful, they may be totally off the wall. Congratulations, on being a mother to-be; and for my part, congratulations on taking an audacious stand on your own behalf.
