Find him something to do and/or get a friend or so to visit often. Possibly Puzzles, going to a community center and doing activities. Maybe he could baby sit kids depending on how disabled he is. If so he could volunteer as a sub at the local Y and thus get a free membership.
I also think that contributing so much to the church without his knowledge is wrong. You ask him not to spend much and then you turn around and give a lot to your church. Is it by chance close to what he spends each month? If so then you need to stop over spending first (I consider giving so much to the church over spendng.). Tith only 10% of your income and you will be following Gods request. That is what the Bible says to Tith (give).
You need to give him an allowance for his spending money. You also should have an allowance. Then both of you can spend it any way you wish, no budget. The rest of your money should be budgeted. (A necessary evil.) Also if you pull out savings first then you won’t miss the money because it isn’t there to spend. Get rid of all your credit cards but 1 main one. Hide it and use it only for emergencies. Cut up the other cards, pay them off then cancel them. Debit cards and checks need to be put away as well.