Congratulations for adopting. Sounds like nothing but good things are awaiting him in his new home.
I recently adopted a 25 year old CAG and although he was great on my visits to the adoption center and his first day home, he chomped me hard in the second day. This obviously broke the trust for both of us and we are still building it back up. It has been a month and we are making progress.
Like you, I began using a dowel rod to pick him up. He would attack that rod with a vengeance. After weeks of this, last night we had a breakthrough. When he comes out of his cage, he likes to go straight to the floor. This is when I usually pick him up to put him on his playgym. BUT, for some reason, yesterday he stepped up on the dowel with no problem at all. No attack, no bites or chomps. I was shocked and thrilled.
As many have said, baby steps. It could take a very long time for you to be able to pick him up but keep trying. Look into target training as this has helped me with Morgan.