I know you just said you weren't going to, but I feel the need to emphasize this... DO NOT. MOVE IN. WITH THEM. The fact they would suggest this highlights how new to poly they are. Greater proximity will greatly exacerbate whatever problems you're having now, it is in no way a solution.
Maybe you could find some articles, essays or other people's personal stories that resonate with your situation and ask them if they would read them. Their lack of understanding is natural but dangerous.
I think you're headed in a good direction with becoming more independent of them.
And as for the boundary breaking, if you're determined to leave it in the past then do so. Make sure you've really, really forgiven yourself and let it go. Not every secret *has* to be revealed. I have a strong policy of honesty, but I do believe that.
Me, 30ish bi female, been doing solo poly for roughly 5 years. Gia, Clay, and Pike, my partners. Davis, ex/friend/"it's complicated." Eric, Gia's husband. Bee, Gia and Eric's toddler.