I'd say that both Swift Concentration and Schism work just fine. Use whichever works.
Weight, go ahead and keep halving it.
Body slots...Hmm. This is completely arbitrary and I may be off my rocker here, but face, throat, body, waist, head, shoulders, and torso.
Just handwave the items the psion is wearing, but for manipulated items, only as many as he could actually hold. So, for instance, two dorjes, one in each hand.