Any ideas...

Speaking from experience, having broken a fair few bones in my time, and injured myself more times than I can remember.....maybe thats the concussions ;)
Doctors always know best, but sometimes they are a little over cautious...
I had much more severe metal work in my femur, mine was removed in two seperate ops, after the first op I was only just about walking anyways so it was no big deal that I couldn't do much. But after the second op I was already well into my recovery, so it was kind of annoying when it hurt like fuck after they removed it, but I was back exercising around 10 days afterwards, and bmxing a month later.
Best advice I can give is don't do stuff thats high resistance, e.g. don't go trying to do any big weights in the gym, no heavy sprinting on the bike, take it easy, little and often is the best approach.
High rep squats with your bodyweight or just the barbell are a good idea, swimming is excellent, getting on the bike should be fine, but you want stuff with a little bit of impact to help the bone knit and to strengthen it, brisk walking is also ideal.
In terms of diet protein shakes are fine, you want longer digesting protein than just the whey stuff though, I would recommend whey protein shakes in the morning and lunch and then casein/micellar casein type proteins afternoon nighttime, a casein based shake, or some natural cottage cheese is excellent before bed as well.
Try to get as much as you can from food sources though, plenty of calcium and vitamin C (both very important), try and eat a generally healthy diet, lay off the alcohol completely if possible, as it will slow healing and certainly aid inflammation.
I found all the above helped me a great deal and I was back to normal in a month or two after the second op (apart from the odd twinge here and there).