"...We should have some recourse, I would expect, as this is pure manipulation..."
You wish, H!
No recourse.
Current manipulation (if that is what it is) falls well within usual market behaviour.
But be aware that sbet firms have some very handy get-out clauses that allow them to terminate a bet prematurely should they wish to. Including anything they decide is "unusual market action". How vague is that?? Or "anything which restricts liquidity, or might do so".