Overheating issue

I have a 2003 BMW 745i e65 n62. Coolant transfer pipe has recently been replaced. Had a coolant leak which was identified as the heater core. Don't have $ for the repair now so I temporarily settled for a heater core bypass for a fraction of the cost. Car ran fine for a few weeks then coolant reservoir cracked/steamed and I can't figure out why. Since then after about 10 min of driving the car overheats and I can hear (hot)Coolant boiling in the overflow tank as well as the engine. Upper radiator hose feel hot, dry, and empty. I pulled and tested the ect sensor (engine coolant temperature (on water pump)) sensor and wire both seem to work fine. Overheating seems to be suppressed while AC is running, then within 1min of turning AC off car overheats. Water pump is not leaking and I don't feel any play in it. Weep hole is dry, but I noticed another coolant leak under their center of the car (near floor of rear seats). I filled coolant, poured coolant in upper radiator hose and radiator to help remove any trapped air and let the car idle. It did well for about 30 min then overheated again. I'm at a loss, help

Overheating issue