I don't mean to oversimplify it, and actually putting "20's" makes it tough to say, but it just really doesn't sound like either of you are ready to be in this kind of relationship, one with marriage potential.

This is completely in a vacuum, what comes later in your post is separate and still extremely valid. But this line struck me as a really weird line, and kind of a general 'red flag.'

A) so dense that he would sink straight to the bottom of the ocean if I tossed him or B) in denial about girls liking him so he can continue to interact with them without feeling guilty. Which is worse I do not know.

It's pretty immature for you to decide that it must be A or B without even speaking to your boyfriend or alerting him to the issue. While absolutely he disrespected you at that party, instead of sulking and trying to 'send signals,' you should have spoken to him about it.

It's also extremely possible that he wasn't quite as brilliant a schemer as you think. Dig up any "What were the obvious signs you missed?" thread from AskReddit. People have missed far more obvious signs than some flirty touching at a party. His girlfriend was right there, so the idea of her actually hitting on him might not have crossed his brain.

Or, very possibly, it's "B" in your "it can only be one of these two" list. You'd have a much better clue if you talked to him.

If the communication was better between both of you, it would likely stop this cyclical dynamic of him hiding things that really aren't a big deal. You let the issue with Becky get pretty far and then it exploded, so he may feel that he can't win: he either gets punished for "being too dense" or for hiding it.