Sweetheart, someday, someone's gonna hoist you with your own spork. 足元を掬われる, literally something to the effect of "scoop out [as with a spoon] your footing" and figuratively about the same thing as "pull the rug out from under," but I think the use of that particular idiom is also referring to Yuuma's weapon of choice, hence the "hoist with his own petard" modification.

And should I bet on your sorry ass being the one to do it?

So basically, I wasn't nuts to think that. That's what that means.

I'm trembling with anticipation!

... This kind of crap is exactly why I just can't stomach you.