I agree totally. The idea of giving 10% is just a rule of thumb in NT times, and does not apply at all to someone who is scraping to make ends meet. If anything, they should be the beneficiary of the "tithe".
Note how it's the yearly increase, not the monthly income. If you make a certain amount in a year, and spend it all on necessities, you have an increase of zero. Only if you increase your assets with that money would you (under the old law, which was nailed to the cross) be liable for anything. Only the "rich" (those with businesses and capital) have increase.