Thank you everyone for your welcome and input.
I keep vacillating between sadness and anger. I guess it's part of the process.
I think the first step is going to be to gather all my notes (in memory, texts, and emails) into one place.
As to a Plan B, my inlaws, etc - I'm really not worried about getting kicked out (I doubt they would do that to their grandkids), but I do have a little over $12,000 saved in my emergency/independence fund. I'm not touching that account unless I absolutely have to - I'm planning to get loans for school so I can keep that cushion.
I would really appreciate advice down the road from those who know more than I do about the whole divorce procedure. I live in Florida.
I'm also trying to figure out what to do with all his stuff, especially now that he's in rehab, and I have no idea where he's going to be living afterward (he was on the verge of eviction at his last place). I don't want to deal with him directly if at all possible - he can be very triggering and hateful when he's angry, and I'm pretty sure he's quite angry with me - the reason he's in rehab now is because I told his mother about a convo with a mutual friend (who lives in the same complex) about how bad the situation had gotten. This friend told me that AH had screamed at her to never talk to me again.
I'm really feeling the weight of all this plus issues with my dysfunctional inlaws (he was on a smear campaign against me for years - he told them things to make me look bad so he could look better, and that has affected my relationship with them).
I feel like I'm blabbing, sorry.