Charge pressure is supplied by the implement pump, the pump your having issues with. Charge pressure supplies the drive pumps with oil, keeping it simple here. Your charge relief should be set between 85 and 115 PSI depending on your serial number. Your drive pumps work in a loop and needs charge pressure to replenish the oil to the drive pumps. Charge pressure won't keep you from lifting or tilting but it's easy to check by plumbing to charge pressure sensor port and look for pressure. The pump supplies flow, restrictions create pressure. If you can remove the main pump hose from valve body and connect another hose to it long enough to reach to the tank, start the machine and see how much flow you have, should be like a strong water hose flow. I think you said it was hard to do because your machine creeps, raise the machine put it on jack stands start the machine and check the flow. You don't have to connect a high pressure hydraulic hose to do this, again the pump creates Flow restriction creates pressure as long as there's no restriction going back to tank you should not have high pressure. I still think you're going to need a new pump however