Your first option is best. Insulting comeback that isn’t open-ended. It ends it so you can move on. The other options are asking for a response, including the OP one.

Are you coming on to me?”

I’ve actually used “I’m flattered, but I’m not into guys, sorry.” and when immediately he got pissy and insisted he isn’t gay and wasn’t asking me out, “It’s okay, you don’t have to hide who you are, I’m simply not interested.” and at that point my patience and certainty they wouldnt try to deck me were out the door, along with myself.

A musical theater performance was probably not the best place for the guy to be attempting to ragebait.

10/10 responses, I’d add in “If you have to ask, maybe you should get out more” which I guess is similar to “Makes sense you wouldn’t know”

You could always go jeopardy style of “what is someone who doesn’t want to sleep with you”