How do you handle a family member who is a substance abuser when it comes to the care of my MIL?

My husband & I have been living with his mother for going on 3+ years. We are her primary care givers. She can not live alone. My BIL has always had "entitlement" issues regarding the "family" money.While MIL still had most of her facellties he talked her into getting a reversed mortage "so he could buy an 18 wheeler" Throught his "it will not happen to me" attitude he got 2 DUI's & a DWS all within a week and lost his CDL & drivers liscence. He has been in & out of the house for atleast several years. He has a siever drinking problem. He was living on his boat and had been "banned" from several bost basins / docks around the mouth of the Columbia River. He has been back & forth from Alaska working (what we are told) in the fisheries. We (Mom) have paid for numorious tickets up & back. This last time he went up he never "really found a job" and we were sending several hundred dollars a month up to him to live. He was "asked to leave" several places :"because of something someone else did"

Here lays the problem. When he drinks; he gets these wild ideas and if things don't go as "he thinks they should" ( we will not take him to the liquor store, or the store in general or the latest "take him to meet a girl 50 miles away") he gets VERY vebally abusive to my husband and myself. Making statements that he is going to call the State about the way things are "around the house" (we live in her basement) Yes, we may not the best housekeepers of our part of the house but everything on the ground floor of the house (where MIL is - she can't do stairs) is fairly spotless. Dishes done, bathroom clean, clothes & bedding washed. We feed her what she will eat. The one thing that is as issue is my MIL hygine. her idea of "taking a bath" is washing herself with a washcloth (which she has forgotten how to do) Her hair has not been washed in weeks; the gal that was doing here hair passed away from breast cancer and she will not leave the house if it is raining.
After he has "Slept it off" he is all apoligentic about it. FYI Christmas 2011 he and a buddy had been drinking and passed out at the dining table; my MIL did not know what was going on and I ended up eating my Christmas dinner alone in the basement.

To top it off we discovered that about the time he lost his liscence and was living on his boat; he took a pad of checks & was forgeing checks with my MIL signature to the tune of $5000 to $8000 dollars. Some of these checks did not clear and my MIL was held responsible for them.

I work fulltime and my husband is with his mother almost allday. From time to time he does get out (mostly to either take me to work or pick me up) the only time we have together is if we stop at the store on the way home from him picking me up. We really do not trust BIL to look after his Mom properly.

HELP WHAT CAN WE DO? Family Monies are in a family trust and tied up. Husband & his brother are co-trustess of the trust.