In need of some advice

I have been MIA for a while, mostly because for whatever reason during the transition to this new format I couldn't get TB to load on my computer. Also, because we had SS4 all of July for our first summer visitation with him. Things went well enough, he of course missed his mom, but for the most part was well behaved and we had a lot of fun. I could go on about our month, but really bigger things have happened since. SS went home with BM on Sunday. On Wednesday she called with some ridiculous medical question and then basically told DH never mind. Thursday morning she called and said the reason she had actually called the night before was because her parents had thrown her and SS out of the house on Tuesday and she was too embarrassed to tell DH, could we please come get SS for a few days. He had spent the two nights prior at BM's aunt's house, but hadn't had a bath in two days and BM was sleeping outside in her truck because her aunt already has multiple young kids she cares for and didn't have space. We went and got SS. BM's parents told her she could come back home on Friday, but she is refusing. She states that the house is not a good environment for SS (we have all known this for awhile, but haven't had enough hard evidence to prove so) and as long as she isn't there, she has motivation to do better for herself and SS. She does not have the money to get her own place. She also doesn't want to legally give us SS.

DH has already told her that she can take all the time she needs to get herself together, but in the meantime, primary custody needs to be signed over to him. As of right now, she seems to be considering it, but keeps saying "I just don't want you taking him away from me. You can just stop sending CS but I don't want you to have custody. etc." DH is prepared to talk to his attorney on Monday and start working things out legally, and has already told BM that "just stopping CS" isn't an option- that we need paperwork so that he doesn't fall into arrears, that we can enroll SS in school, that she can't just show up 3 months from now and uproot everything because she finally got it together, etc. He has said he will work with her on visitation, he doesn't want CS from her, and that once she is back on two feet, with a stable environment for SS, he will work with getting SS back to her, as primary, if it is what is best for him at that time.

In the meantime, I feel so overwhelmed with everything that needs to be done. School starts in 3 weeks and I just now today looked at preschools in our area- which all have wait lists (we've spent the past few months researching the ones near BM with the expectation that he would be there). SS is beyond angry and for the first time told DH and I today, using his words, "I'm really mad at you and Daddy because I want Mommy and you took me away." He is acting out, blatantly defiant and argumentative, and just angry in every way that 4 year olds express it. I know he needs to be seeing a therapist for help processing all of this, but I don't know where to start. We just changed his pediatrician to one close to BM (2hrs away) and got his school shots taken care of while he was with us in July. The pediatricians by us have a month long wait list to be seen, if they will even accept new patients on our insurance, which most won't. I feel like there are so many important things to take on and I don't know which to start with or where to go next. Part of me says don't even bother with preschool until we get all the emotional/psychological things at least addressed, but between our jobs, we wouldn't have much of a choice, SS will have to be in preschool, daycare or with a babysitter at least 3 days a week. How does therapy work? Do you go through the peds office first or can you just call up for consultations? Should we even start with working these things out before the CO has been revised? Would preschool be better to provide something consistent and a distraction or too much stress on top of everything else? Any advice welcome. TIA

And a small FF rant- We are also pretty upset because we have been planning a trip since February to Alaska- tickets paid for, day cruise booked, zip lining in Denver during our layover booked, hiking gear purchased, PTO approved, $1000's spent, and we are supposed to leave Wednesday for 10 days. I know it's petty compared to the much bigger and more important things going on here, but I am pretty upset about having to cancel everything because of circumstances outside our control.