For the spitting I would encourage him to do something else with his mouth. Ie. Clicking his tongue or making funny sounds or rolling his R's (if you can - I did this with ds around this age). I do this whenever ds grinds his teeth and it has worked well to distract him.
Good idea!! My daughter went through a teeth grinding stage. Not naughty, but horrible to hear and I she did it with such force I was worried she'd do damage. I didn't want to comment on the grinding itself, in case it increases the behaviour. Instead, I'd ask her to show me where her tongue was. She couldn't grind and poke out her to for at the same time!