Why 100psi? The max pressure I can find for any of the rockshox or FSX/Future shock service manuals is still under 50psi so 100psi would effectively lock the fork out.
I blew apart the fork legs again yesterday to see if perhaps I'd missed something and I dont think so - as I was filling the fork up with oil and cycling it, it seemed that the closer I got to a full oil level, the more likely it was to bind up and stick at the bottom of its travel. So it sort of feels like a hydraulic lock, but, it could also be binding. One of the fork legs took a significant amount more pressure from the floor pump to separate the lowers and the same fork leg required some persuasion to seat the bushings into the lowers. Once in, it moved really nice though, so I wonder if with the fork brace and wheel on something is causing that leg to bind.
With no history and obviously someone in there before adding o-rings that didnt belong (and it was very low on oil) who knows what happened to it in the past.