Give him as many power points as you can; also, beef up his Hide skill, and take chameleon and the Darkstalker feat (can't hit what you can't see).
Furthermore, grab greater concealing amorpha as soon as you're able, because then you will literally be unable to be targeted by any effect that doesn't specifically affect an AoE or that requires an attack roll (and you still get the miss-chance).
Metamorphosis and the Metamorphic Transfer feat (and Assume Supernatural Ability, from Savage Species) will grant you things like the pixie's at-will improved invisibility. You can also use metamorphosis on your psicrystal for some interesting means of self-defense, such as turning it into a giant crawling hamster-ball that shields you from harm (you can do something similar with psionic minor creation, by the way, though it won't be animate).