Here's a good link on seperation anxiety:
http://www.hsus.org/pets/pet_care/ou...n_anxiety.html

I don't think it's possible for him to go to doggie daycare until his treatment is well over, if he gets overexcited he can actually go into cardiac arrest.

Good luck with him. We used to have a beagle that had SEVERE seperation anxiety to the point she was hurting herself trying to go through walls and windows. I was really young and my parents didn't have a clue...it wasn't a good ending for her, but hopefully with the more advanced knowledge of today and with someone willing to take the steps, it should work out okay.