Dash AC not cold

I'm wondering if my expectations for my Dash AC are set too high. It just doesn't seem to blow very cold. When it is about 85 out it comes out about 63 out of the dash with an AC temperature gauge. I tried it on a rental car and it was coming out like 50 degrees at the same time for the rental. Never had any luck doing AC pressure readings but I did buy a gauge set. I hear if it has an expansion valve you can't get quite the right readings but then I also read that if the pressure isn't changing on the low side then you have something stuck or plugged and I'm not sure what that is.

At 85° I get a pressure of about 255 on the high side which appears from when I'm reading to be accurate but the low side is just 15. No matter how much Freon I put in there the low side pressure doesn't change and the high side pressure goes up and of course I have to evacuate that because it can't be too high I don't want to ruin the compressor. Also not sure what type of oil to put in I believe it's some kind of 46 oil but there's no real accurate information to confirm that there's a bunch of different oils. The compressor appears to be engaged fine. I did notice when I put fluid in you could see a little tiny bubbling from the high and low sides I tighten the needle valve down. This could indicate some kind of bad o-ring or needle valve that needs replaced I did put a new needle valve in one of them but I think it still has a little bubble where the needle valve is I think it also goes away though I guess when it gets agitated or something maybe they can bubble out a little I'm not sure. But this could indicate a separate problem I think regardless of the needle valve when you put 5 lb in there the pressure still on the left side never goes up above 15. So like I say two different advice that I saw on forums were that something is sticking cuz it should go up between 30 and 50 psi but then a contradictory for him said that because it might have an expansion fitting that it never will fluctuate or something but it just seems too low for me.

I can't find an AC place that will even look at it because it took camper and a diesel pusher. Maybe 63°is a normal reading with the compressor way in the back. But I really have no information on the routing or any of this for this it would be great to get a diagram of how it's routed and how many pounds it would take I mean I'm guessing it's about four to five pounds somebody said on some forum somewhere. It is r134a system.

This is a 2006 Monaco executive with a 525 horsepower isx15 Cummins engine that was supposedly upgraded to 600 HP on a Roadmaster
chassis.

Sorry for the long post but at least it's a full explanation hopefully. Not sure how to add pictures I don't see that option maybe I'm too new. Oh and most forms people don't post their solutions which drives me crazy so I promise I'll post a solution if I find one or what the final analysis was for example on the low pressure.