D.B.
I would meet with a financial planner to separate your accounts - set aside what you need for retirement income, have another account for current household expenses (mortgage, insurance, utilities, food, repairs and all of that), and then set aside a small amount of discretionary income for each of you (that's 2 discretionary accounts). You control yours, and he controls his. When his discretionary account is empty, then he's done for the month. If he gives his golf or vacation money to the nieces and nephews, that's up to him, but he can't divert money from the other accounts. If he believes their lies, that's his problem. But it will no longer be your problem. You can use your money to go on vacation (without him, because he's out of money), or to get together for spa days with friends, or to take come fun classes or whatever pleases you. He doesn't get to go on these things on your dime. He needs to feel the pain of giving.
I echo the idea that you should meet with a pastor or priest of your husband's religion to get some clarify on what God expects. Most religions teach the importance of charity to the truly needy, but that doesn't mean giving to anyone who asks. It means making responsible choices. It also means not handicapping them for the rest of their lives by not allowing them to be responsible for themselves and know the joy of success.
Stop having discussions with his family. They aren't your problem. Your husband is your problem. They could not take advantage of him without his permission and participation. What you need to do is protect your own financial future (and "saving a bit for retirement" isn't enough), whether he agrees with you or not. They'll (hopefully) stop hating on you if you stop getting in their faces (you're justified, but you cannot win if your husband isn't on your side). You can be pleasant at family gatherings, or you can get up and go get another plate at the buffet table if the discussion turns to money. If you need to say anything, just say, "I'm going to excuse myself from private financial discussions." If they are still brutal to you after 6 months of not engaging with them, then stop going.
Once you get this squared away, I'd suggest that your children meet with a planner too. They need to learn to safeguard and manage their earnings, and they aren't going to learn this from your husband. And if history is any predictor of the future, these relatives will start on your kids when your husband is dead or broke.