I did the approach, which went well

I was getting ioi's and she wanted me to flex so she could feel my bicep, I think I played it off the wrong way and said "I don't flex for just anyone, your gonna have to pay" she said stuff like "come on, just once" and kinda begging me a little.

Later on I escalated with some pretty serious leg touching under the table, and I played with her hands when I pointed out her bracelets, she resisted a little to that. I also gave some sexual eye contact in where it seemed she found it a little difficult to look me in the eyes. Overall it went pretty well.

Should I had let her feel my bicep or touch me in anyway or should I continue to play the irresistible asshole?

I don't think you should have let her touch you, it's too close to the dancing monkey stuff. Maybe you should have teased her a bit about what kind of a girl she is, being so superficial and you're more than just your muscles blah blah and maybe insinuated if she behaves she gets to touch you later or something like that. But I'm sure you'll get more qualified opinions from the other guys.

You should have said "sure, after you. Ladies first .-then possible neg on her flexing" What she did was present you with a hoop to jump through. If you had flexed your biceps, you would have jumped through her hoop which tells her she has a higher value than you. When she presents you with a hoop to jump through, you present her with another hoop. Generally speaking, only jump through her hoop after she has jumped through yours. However, this should be done very playfully. Whenever you neg you have to make sure you're being playful.