If it takes you 30 min to start overheating, then that is puzzling. A therm stuck closed would probably take less than 10 minutes to overheat as would a bad water pump. Is there any fluid lealking from the water pump? Either way, I would recommend replacing the therm and water pump. Once they are removed, flush out the radiator.

Have you tried bleeding any air out of the system? There's an air bleed screw for that.

Have you checked the oil to see if you have a head gasket leak?