Here's what I think:
AC Bonus (Su): Considering you could be wearing full plate instead of doing this I have no problem with this
Bonus Exalted Feats: I don't know too much about the exalted feats but wouldn't this mean you would have to pick more feats from 3.5. This could get complicated so leave it out.
Endure Elements (Ex): Not that great. This would be useful if we had rule for climate in the specific regions of Calidor
Exalted Strike (Su): A 20th level character with a +5 weapon, got no problem with that.
Sustenance (Ex): Neat, but insignificant since to my knowledge food isn't that hard to come by.
Deflection (Su): Once again I have no problem with you getting any armor class bonuses from this
Resistance (Ex): Like you said, a 17th level character could easily get a cloak of resistance +4
Ability Score Enhancement (Ex): Ridiculously powerful but when I consider the trade off I'm willing to tolerate this
Natural Armor (Ex): No problem
Mind Shielding (Ex): Very minor.
Damage Reduction (Su): A solid ability, but still within reason.
Greater Sustenance (Ex): I can't see a lot of situations where this would be useful (in this campaign at least)
Energy Resistance (Ex): Not bad, but nothing game breaking.
Freedom of Movement (Ex): Holy crap that's good!
Regeneration (Ex): Minor
True Seeing (Su): An 18th level character has easy access to true seeing, no objections here.
I'll let it pass, but get rid of the Bonus Feat and one of the following: Ability Enhancement, Damage Reduction or Freedom of Movement.