I see you have been using teething tablets, tylenol and such. Have you tried Humphreys teething tablets? I was told to use them when my first was teething, she's 18 now, and I lived in a city where they were easy to find, but recently, with my last 2 children (now almost 9 and just turned 3), I can only find them at K-mart, and they had to order them for me.
They are little round tablets that melt quickly and taste like sugar. They are a homeopathic remedy (which I know nothing about, but I do know they worked without unnecassary medications)
Another thing you may want to try is ice pops - they are not just for summertime. I cut one in half, then wrap it with a napkin so it doesnt freeze their little hands. These are good for numbing just before eating meals.
I know that nobody wants to intruduce a pacifier when their child doesn't take one, but it may be good for him to chew on - it will put pressure on the gums and try to push the teeth out a little faster, and massage the gums at the same time. Or something soft plastic to chew on. I bought my littlest one new ear bulb syringe - like what they use in the hospitals for the nose, but smaller - for her to chew on.
Sorry, a late thought. How about a dry wash cloth. It will give him something to chew on, and soak excess drool.