I have gauges and had them hooked up and it is pretty much the same as yours. 30LP and 250HP. It does take a while to equalize but I think after about 2 hrs it is equal. I have watched my gauges as I rev the engine to 3k and the HP works about like a tach. It increases up to about 350 and then slowly comes back down to 225ish. I have checked the gauges when it is not blowing cold but the compressor is running and they indicate low freon 35LP/150HP. But then 30min later it works and blows 30*F air.
I think I may be headed down the same road as you and replace a bunch of stuff. Since you have it all open why not just replace the compressor too?
2004 330i ZHP