You just have to be principled. Here are some simple principles.

(1) Unless you are dripping off wealth (Fu De Mao You:-), you are never going to be an inexhaustible resource of the relatives' finance. That has to be understood between all parties, including your husband who is eager to help his side of the family.

(2) At best you will be a source of supporting their emergency or critical needs, not their everyday livelihood.

(3) But as christian you are not exonerated from caring about their less than desired well being due to poverty. Try to take advantage of the living standard difference between them and you, and budget a fixed (but yearly increased) amount of US dollars for continuous support first to the elderly parents, then to the needy school kids. Better yet, read point 4 below.

(4) The best support is always those that help people to be self-supporting, reaping a multiplicative benefits. I suggest that you look into their lives and see if a small loan ($10,000-20,000) will help most relatives to start a local business. I suggest the idea of loan so that they are accountable before your family and they will not easily squandered away the money. You wish to see them to be well to do by their own diligence and business so that you need not have to constantly worry about their financial needs. Believe me, this is the best idea I can give you.

You may think the upfront loan is no small money to your family. But calculate this way: if you continue to support them at an average of $2000 per year in the next ten years, the $20,000 you will have given them will certainly have benefitted them in some ways, but the money are gone forever and you probably need to support them in the next ten year after that. It is far better to give them a lump sum as a loan (see reason above) now and take the risk of helping them start a low-risk business that will sustains them many years due to the profits and interst compounding effect. Guess what, as the wise investor you are free to get the loan back (I am sure they are happy to do that too) or leave for their benefits (which will delight them). It is a win-win case no matter how you do.

(5) As for tithing, you need to seek a common understanding with your husband since the Lord delights in a cheerful and sacrificial giver, not offerings that are given out of duty and without joy. Thus, instead of giving to the Lord less than cheerfully and sacrificially, I suggest that you decide with your husband what amount can be given with great joy and a little sacrifice.