Building savings for ALZ father?

My father has been diagnosed with Alzheimer's. Since divorcing and then reuniting with my stepmother 10 years go, he has been living with her in Florida in her condo (no mortgage and he has no ownership in it) and she has been his caretaker since his condition began a couple years ago. Recently, she agreed to care for him until she couldn't anymore and transfer to a facility was necessary at which point she would move to NY to be with her kids. He is getting to that stage and his 5 kids are arranging his move to AZ to be closer to us at a TBD Memory Care facility. With recent access to his bank records now, it's clear that his ex-wife has been taking $1100 of his $1800 SS check every month by bank draft even though they have no mortgage and live in a small condo. (I suspect she's banking that $1100 to live on when he goes into a home, leaving him with nothing). What he has left pays his car payment ($380), insurance payment ($120) and his cremation plan. The remainder goes to dog grooming and eating out here and there. He has $5.03 in his savings account...$5 being the minimum required to avoid a monthly fee. He has no assets. When we sell his car, it will just pay off the loan.

Until he is relocated, we want to take some of the $1100 she has been taking and put it in a savings account for him so he has some money for incidentals once the Memory Care facility starts taking his SS check, and also to help cover his eventual funeral expenses. Two of us are co-executors/POA for Dad. None of expect any of this money to split someday...we just don't want to have to put out thousands of dollars for his funeral which will likely take place in NY, where the extended family lives.

What's the best way to manage setting up an account that won't be taken from him by Medicaid (assuming he qualifies), or that will not put him over the threshold for various assistance programs? His monthly income puts him just under the cusp of several programs he may qualify for. Any ideas for small savings shelters would be appreciated.