First of all, they can't change your pay retroactively. So they owe you commissions from January until now. They can change your pay going forward, and at that point you can choose to walk away. Commissions are absolutely part of your wage and you can go after them for wage theft. Bonuses may not be part of your wage if they are at the discretion of the company and not tied to objective measures (e.g. a holiday bonus). But if the bonus was based on the company hitting certain milestones (e.g. profitability) or was stipulated as being offered without any conditions, then they do owe you the money.

I can't imagine you'd have a pleasant time with an employer you sued for wage theft, and the signal is pretty clear that they're not going to match your previous commission structure, so if I were you I'd be looking for a new job with an aim to filing a DOL claim once you have that new job.