You could give him the Robe of Shadows to make him ethereal, if you can make it, and have him cast Ironskin to give himself protection 20 in battle. If he had a pendant of luck as well, he might be reasonably survivable. Casting fire shield would probably stack with his natural fire shield as well, which would be brutal. His main problem is a lack of hit points - sooner or later a hit would get through, then it'd be no more Anointed
.
Defense isn't so key really. In battle every attacker after the first gives -2 to defense, so if he ends up fighting a crowd then most of them will hit him whatever you do. The trick is to make their hits not count for anything.
Reinvigoration is a good point. An amulet of resilience and boots of the messenger would do a good job. Then so long as it took more than three or four rounds to kill him each time he'd last forever.