Absent a written contract or collective bargaining agreement to the contrary, employers can prospectively change the compensation they offer. They can't change past earnings, but they can announce a new system of pay going forward. If you're an employee they must pay at least minimum wage. I do not have any ability to review your pay history to see if there's merit to your former employer's claim that he overpaid you, although despite your claim that "he sues everybody" I am skeptical that he's going to sue you over $162 if that is in fact the amount of the alleged overpayment.

I'm not clear as to whether you're stating that in January you were told that you were going over to commission-based pay, or that your employer attempted to retroactively recharacterize your pay as commission-based. If it was "from that point going forward," again, that's permitted. If he in fact told you that he was "no longer paying a salary", I can see how a misunderstanding might arise in relation to the additional pay; but I'm not certain at this point if you're claiming that he misrepresented something or if you misunderstood what he meant.

I don't know what you mean by "Can he take wages earned from last year that were reported to the IRS on my W-2". If you were paid, you have that money.