Arm pump is an issue of cardio fitness, relaxation, technique and nerves. Don't freakin smoke, that will shut down your veins too.
Your bones get beefier through resistance and stress--weight training and plyometric, the "pounding" stuff.
James had the smashed collar bone, right? My kid fractured his(just got a sling). He's taking Vit D, calcium and drinking milk and eating dairy etc(stuff with calcium). He's also sitting in the sun for 15 mintues or so. It's been 4 weeks, and he just started riding his bike(mtn bike w/suspension)--it seems he can do that without much pain.
I'm not sure on this, but I think if you do something like running it will have a bit of residual effect on the whole of your bones--your legs/pelvis/back will be stimulated from the pounding to get denser, and I think maybe just your whole skeleton might be buffed up a little bit because the bone densifying engine is revved up for the legs/pelvis/back.
Can you do something like a farmer's carry? where you just carry heavy stuff around in your hands(like 2 buckets full of heavy stuff). It would put a little force on your shoulders without making the joint move--just stress them a bit to stimulate the beefing up, and it's great for grip strength. When you can do them, pushups and chin ups would be a great thing too.