It does just sound like an easy solution doesn't it...just say no?
But when he's really into it he's not listening to me.
I think you're right and I need to ramp up the severity of my 'no'. What works when he gets to chewing on me too much is a stern no and a push down onto his back (gently of course) and hold him there for a few seconds with a growl. I'll try that with the jumping up.