Self employed

I qualify 100%, however due to the limit for 1 dependent and married filing jointly, apparently I make too much. Who and how is that amount that has been chosen?  It makes no sense whatsoever, seeing as I’m struggling to make ends meet because I am the only one supporting not only myself but my daughter and my husband who doesn’t work & who has heart failure. I am at a loss how this is possible. 
However, I appreciate your input.