Thanks everyone.
Its been such a frustrating and upsetting process but things are definitely improving. I was not able to have zero response, but I did manage to respond without jumping or yelling, just quickly and firmly removing him and setting him down and I think it helped. The joy seemed to go out of the whole enterprise for him, which was a relief.
I don't know why, but the night after I wrote my second post, when I was absolutely at the end of my rope, that night he didn't bite me at all. Maybe he realized I was about to cut him off

. So after that night I was able to relax a little and I think that helped a lot. I think my nervousness was preventing the milk from letting down which was frustrating him and making him bite me and so on. So once the cycle broke things improved. He has bitten me a couple of times again but its much better.
He has been pretty crotchety lately too, like you say, Sammymama, (this boy is also named Sam, funny!). He wants to be held, he wants to be put down, he wants to get into everything and he never wants to sleep. I guess he's going through some big growing and he's figuring it all out.
He is still biting everything else around him but when nursing he's started something new, when he's done he leans back and opens his mouth really wide and grins at me. So I guess he got that much.
Thanks everyone for the encouragement. With this one, and with my daughter before my period came back really early, even with constant and exclusive breastfeeding, and once it came back the hormonal fluctuations play havoc with my supply. Combine that with the biting and I just started to feel like it was more than I could handle. Right now I can carry on a while longer. I don't think we'll make it to 2 1/2, but I hope we can make it to a year.
Thank you all.