2004 X5 E53 4.4i A/C System Mystery Problem

[X5StayinAlive]

Hi group. This is my first post. Sorry it's such a long one. Thanks in advance for any help. I'm hoping someone has crossed this stream before and can guide me further. I have a 2004 X5 E53 4.4i with 207k miles. Seller said It was heading to the scrap yard if I didn't buy. Lots of my sweat equity into this thing. I'll post picture sets of my restoration and light custom touches in another post. But my question of the day is about the A/C system. It didn't work when I bought it. It had an unknown R134a charge that never leaked or lost pressure. I've just dived into resuscitating it. Pulled a perfect 30" vacuum that it held for 2 days. No leaks. Charged it with 440 grams of R134a. Also added lube agents. NO Stop Leak added. There are No leaks. Manifold Gauges read 55psi low side and 210psi high side. 24 Degrees F at center dash vents. This is with direct sun and 85+ ambient at Sea Level in NJ. Sounds Great, right?? It is great until engine goes over 2000rpm. Then the low side goes to about 80psi and high side about 110psi. Bye bye cooling. It's not an overheat issue. It will idle all day from cold start to full engine temp if left alone in the hot sunshine and chill the inside great. Drive it and pass 2000rpm.... No more AC cooling. And it does Not start cooling again once 2000rpm is crossed, and then back to idle again. Needs to be left off overnight. Then cools perfect again until next 2000rpm crossing. I changed out to a new TXV valve thinking that was it because slightly slow return to equilibrium when shutting off system while working well. Exact same issues. No ugly black death oil residue anywhere I can see. Static pressures in morning when off overnight are equal and temperature appropriate. Compressor clutch never seems to cut out.

When I installed that new TXV it helped, but didn't cure. I did not replace the desiccant, as the system has never been opened except for quick TXV swap. Then immediate 90+ minute vacuum. Powerful 2 stage 8cfm vacuum pump. Good gauges. No leaks.
Radiator, condenser, oil cooler all clear and squeaky clean. No obstructions.
INPA shows no error faults. Electric fan and AC clutch engage in use, and on software command from INPA. But if I force AC into 2000rpm+ failure mode, fan will not run from AC calling for it. Only engine temp activates fan if needed.
See how this gets tedious? I'm trying to be thorough, but I have to be missing Something.
Another thought to maybe ponder...
This system takes a really Small amount of R134a. 440 grams +/- 10 grams. I am filling this by using a pretty good digital food scale on tare setting to read out Net grams. On a 4 pound system, close enough is good enough. On this E53 requiring 0.97lbs (440 grams) I could easily be over, or under the 10 gram margin of error. Can overcharge or undercharge trigger this failure mode??
And Why does it stay stuck in near equal low and high side pressures until a full overnight rest?? Then back to crazy icy cold. Is there some safety valve / sensor I'm not aware of tripping and staying tripped until car and system is all back to ambient temp again?

Some have recommended a new compressor. I also suspected the compressor. But if it is as they say that it goes weak at higher RPM's, why doesn't cooling come back again at low rpm's or idle? I just drove it again tonight after posting my problem. It blew ice cold 23 degrees at center vent the whole time up to the magic 2000 rpm's of death mark. I even shut the car off in a parking lot for 10 minutes after that happened. No recovery of system cooling. Since it has a magnetic clutch, I'm assuming it is Not a variable displacement type. Nor has any internal pressure regulating valves. I listened to the compressor with a mechanics stethoscope and it didn't sound like rocks in a blender. Just what I thought was normal pump sounds pre the 2000 rpm curse. I haven't had the opportunity to listen with steth after the failure mode occurs yet.
This is my first actual 'car' since losing everything in the SANDY Flood of 2012. (I only have a very used 2001 Ford E250 van since so I can get around and work too.) So I'm not in a financial position to throw parts at it. Is there a definitive test to say Ahhahh! Definitely AC Compressor!? Or whatever else it could be???
I have to admit that this 2004 old tech car designed in the mid to late 90's is frustrating to diagnose.
What am I missing?

Ideas??? Please 🤔🙄😳
Thanx!