On an old car I had, once I had good pressure one minute, then rapidly dropping pressure until it hit 0, never to return. A little piece of debris was able to fit through the filter screen at the pickup. The debris lodged into the lobe of the pump, causing the pump to seize up. This torqued the drive shaft so that it broke into two pieces. While I had the pan off, I replaced the pickup.
I'm betting that the difficult starting is separate from the oil pressure issue. My recommendation is to see if you can find a root cause of the oil pressure loss, then tackle the starting problem separately.
Bill
