Yes, it looks like MBD. Soft or broken bones in his legs, and shaking are symptoms of MBD. You're not giving him enough calcium. It's recommended to give calcium without D3 everyday, calcium with D3 twice a month and vitamin supplements twice a month. I'm don't know what kind of UVB light you're using but UVB is essential for calcium uptake. Make sure he's getting enough UVB. Real sun light would be beneficial at this point, along with a visit to the vet-maybe some liquid calcium.