2000 villager AC problem

I had a leak in the AC system at the bottom of the receiver/drier where it rusted through. So I ordered a new unit and installed it. The o-ring was too small and it leaked again at the coupling by the low pressure port. So I vacuumed the system out again and recharged it with 3 cans of refrigerant(needs 3.5 lbs). Now it seems strange because the front vents are not as cold as they should be. There is no more leaks and I noticed that the receiver is not ice cold and causing condensation like the low pressure side coming from the rear AC unit. I pulled the pressure switch from the top of the drier and the AC turned off which tells me there is pressure in the system. Is my receiver blocked and how can that be? HELP!

* Pressure is 25-35 lbs with AC on. when I turn it off the pressure rises to 75 lbs. That seems normal. So do I need more 134a added to it? I'm probably wrong but I assumed that 1 can = 1 pound.

Doing a little basic math, it appears that I am 1.5 lbs. short.

3 cans is far enough. It's not good too much too much freon, it can kill the system and freeze inside when it's running. Especially if you fill it in one shot.

Normally pressure should be around 40-50 psi when is about 80°F outside. 75psi at stop is too much.

Not sure what is the problem, but don't add more.

Update: I added 1 1/2 cans to the system and sure enough the air started blowing cold again. The problem was low refrigerant. With the front and rear evaportors on the Villager the system needed a full 3.37 lbs of 134a. I only had 2.25 lbs in.

*the compressor on/off pressures on the low side when I was done were 35/65. I don't have a guage to measure the high side unfortunately. Now I hope it doesn't leak anymore. This has been a battle since November.