Am I WAY too far behind in math to go to public school!?

no, you know the fundamentals. you can quickly build it up by going to school, even if it will be hard at first. for example, i recently moved to the US and thus the whole system and order of learning things is different from what i was used to. the first day when we went through what we should already know i stumbled upon quadratics. i really didn't want to continue in honors, but it turned out that it was simply a formula that i had to plug in values, and after that, simply do the basic stuff that you said you know. you will be fine, especially if you are only having trouble in one subject.