with the engine cool/off, remove the thermostat filler and start her up. As the engine heats up enough, you should see fluid going through to the radiator. If you don't see water pumping through, the water pump isn't doing its job.
But, the way you describe the radiator getting hot suggests to me that the pump is pumping hot water into it, so maybe the pump isn't the problem.
maybe time to start at the beginning stew, work through what you know and what you don't know and solve it by a process of elimination.
hot radiator means water is being pumped through it and therefore thermostat is opening. Turning on the electric fan and seeing the engine temp decrease means the radiator and fan are doing their job. More or less efficiently. Seeing low temperature at cruising speed is also good, since it means airflow is
cooling the system down. Having water move into the expansion bottle is normal, particularly if you are idling a hot/worked engine in 27 degrees ambient temp. It is also a sign that you don't have any other leaks. Where do you want to go from here ?
stu