Your argument seems to be roughly equivalent to this: "The term 'tithe' was originally applied to something more like tax than like charity. We pay quite a lot of tax. Some forms of charitable activity turn out to be harmful. Therefore it is not a good idea to give 10% of your income to charitable causes." But that last bit (which is, of course, the point) seems like a total non sequitur.

I see only two things in what you've written that come anywhere near arguing for the final inference. I don't think they're good arguments.

• "Wouldn't changes to government and taxation be a better service for society?" (My answer: They might be a very good thing, but I don't see how they funge against donation to charities.)
• "I fear that adding charity juts skews the existing systems and adds an additional element the effects of which nobody sufficiently understands." (This seems like a universal Argument Against Any Institution. Why is it any more reason to distrust charity than to distrust medical insurance, or banks, or marriage, or armies, or universities?)