2006 Durango (4.7l ) overheating on highway

Been working on this for a while. I think there’s a small coolant leak underneath, haven’t pressure tested. Flushed out some rust. Lower hose not collapsing. No heat coming from heater core and blend door works. Replaced rad cap first. upper rad hose hot. Rad seems to flow. Bled air out the plug. After bleeding air out starts spitting water out bleed plug hole and boiling sound from engine with rad cap off. Spouse said gauge was staying at 5/8 instead of normal 3/8 . replace water pump or thermostat ???