You need to add more R whatever (12 or 134a) to you system. It is normal for high and low sides to be nearly equal after system has been off for a while and cool. If you are pulling negative pressure on the suction side, you need to continue charging the system. At operating temp, the high side should be at least 250psi or better. Low side should be at least 35-45psi (with compressor running). If you are losing pressure, then...you have a leak. Depending on the state of the refrigerant charge, the ambient temp and the system temp, you may see bubbles in the sight glass or you may not. Remember, if system is hot, pressures will be higher on both sides and vice-versa. Overall, you pressures are way too low. Doubt the compressor is failing. There is a good differential between high and low sides, so expansion valve seems to be with you.
2000 Dodge Grand Caravan SE
No matter what you fix, there will always be something else to fix..
"Warranty" is just another way of postponing the inevitable.