You need to have your husband and FIL file the Baker Act on your MIL. She is sick and cannot handle her own affairs... she needs to be institutionalized where she can get help 24-7. Call senior services and tell them what is going on and find out how to go about getting her where she can get...
First of all... don't allow yourself to be baited into a fight.
Secondly, you need to intercept all financial documents to present as proof in court. Let the judge decide.
Hit the bookstore and pick up the latest do-it-yourself divorce guide for your state... you need information.
Check with...
You need to bring everything that can be used to illustrate what all happened... let your lawyer go through it and weed out the excess.
The other lawyer is not going to grill you... he will ask a bunch of slanted questions that you will have to answer "yes or no" to... and your own lawyer will...