I am sorry that this happened to you.
Telling you that he'd ask for a date if he wasn't married is a clumsy way to ask you for a date. The nice way out of that is to pretend it is a clumsy compliment and say "Thanks, but you're not my type" or some such brush off. The important part is that he understands that you mean no.
Asking to feel you up is way over the line. There's no "nice" way to deal with that, and you shouldn't try. Again, it is important that he get the message that asking is inappropriate. "Don't even think about it" is about as nice as you want to get, and it would be perfectly appropriate to apply more anger.
From his point of view, he was trying to see if you had boundaries and if you would enforce them. If he gets the idea from your response that you have no boundaries or that you will not enforce them, he will try again.
I can understand not wanting to get HR involved on the first occasion. But if it happens again, that is persistent harassment, and HR should be involved.