First of all, for you and Bodie. I know exactly what you're feeling because it is very difficult the first week or two. I think they do know that their leg is missing and they are emotionally upset as well as in discomfort physically. Snickers would scream for long stretches and we'd agonize because there wasn't anything we could do. She had a front leg amputated too. I thought that maybe it was her neck muscles because she had to develop a new way of walking, which involved bobbing her head up and down. She really seemed to like that (massages) and would just stand still while I tried to loosen her muscles. She would frequently turn and look at her stump, and it really made me feel guilty. You can't explain that they had a tumor and it will help them.
Don't second guess your decision. Given the same set of choices, you'd make the same decision because amputation does alleviate the pain of bone cancer and gives your pup the best chance of survival.
After a rocky first week or two, during which we had a huge panic where Snickers's remaining front leg filled with fluid and started seeping seroma, it did get better. Snickers also rested in a remote room and didn't have much to do with any of us for a few days too. But after a few weeks, Snickers turned into her old silly self, happy and ready to go for walks, get treats, playing with the kids.
I don't know about the pain medications and what works because Snickers had the strange screaming episodes. Some people suggested garbantin (I think?) for the phantom pain. Maybe the doctors at OSU can work with you on that. Some people suggested a reaction to the Tramadol.
I'd look into local chemo as long as you find someone qualitifed because the car ride does sound long and Bodie's amputation site won't be 100% healed. And then maybe once it's healed, return to OSU for subsequent treatments. It will be very difficult for you to drive all that way if Bodie is uncomfortable.
Hang in there. It's so so hard at first. You have some wonderful happy times with Bodie just arond the corner. You are a wonderful mom to give this second chance to Bodie.
Don't hesitate to ask questions.