He was trying to be funny by making a point that he was now engaged and off the market so to speak. (Engaged to Katie Perry) Now, he can't have sex with other people, so he was bragging about how he should have nailed Sherry when he was there on his last visit and now it's too late because of his engagement. He came off as if whether it happened or not was HIS decision, not a mutual one. Sherry finally told him that it was never going to happen. I think that she may have flirted with him the last time he was there, but that doesn't matter. He was too presumptive.
I think looking grubby is his thing. He's probably clean enough, but just likes to look that way. I think he would soooo different with a haircut and shave.