I read through the thread-- sorry to hear that this is happening to you and your DH. Unfortunately, it is very common.
I'm an employment attorney (or was, before I decided to SAH!), so I just wanted to post a couple of suggestions (disclaimer: this isn't legal advice, per se, since ethically I'm not allowed to give advice over the internet).
First, from what I've read, your main claim appears to be a FMLA retaliation claim, i.e. DH applied for FMLA leave, and bosslady retaliated against him. FYI-- you do NOT need to file with the EEOC to preserve a FMLA claim. You can simply proceed with the claim just like any other lawsuit. The statute of limitations is, I believe, 2 years, so you aren't bound by the 300 day rule that applies to EEOC claims.
Second, w/a FMLA claim, the most important thing DH needs to document (aside from DS's disability) is that he provided notice to his employer that he needed FMLA leave. The Courts have interpreted FMLA quite broadly, meaning that FMLA is very employee-friendly, so DH's notice obligations aren't that onerous, but he will need to prove that he gave proper notice. "Proper notice" varies depending on the situation, but I would make sure DH has all his paperwork (i.e. emails, memos, etc.) in order so that he can establish that he gave proper notice.
Finally, and this is really why I posted, even though FMLA doesn't require an EEOC filing, you may want to go ahead and do one anyway just to make sure all possible claims are protected. However, I strongly strongly urge you to talk to an attorney BEFORE you go down to the EEOC. The intake officers at the EEOC are NOT attorneys, and they don't always take down the information correctly. This is a serious problem, because you as the plaintiff are bound by whatever information you give to the EEOC-- meaning, you can't later add a claim. Consulting with an attorney before hand will ensure that DH knows exactly what claims to make to the EEOC, and what specific information to give. In fact, I often give my clients a typed out EEOC statement, which includes all the relevant claims and facts, so that there is no possibility of confusion.
HTH! If you have any other questions, feel free to PM me. Good luck!