GMB is a good brand. How has your water pump failed? Cooling system pressure is regulated by the radiator cap, so should never see over 15psi.
Contrary to popular belief, even cruising at 100kmph the fan will often need to come on in temps as low as 20 degrees I’ve found. This is a problem pretty well applicable to thermo fans. A poorly performing clutch fan will still move enough air at speed - and I assume this is why people try to diagnose their cooling problems by assessing the temperature at highway speeds. This is compounded with new cars having even more obstacles for ram air to flow around.
When the fuse blew for my thermo fan over a year ago, the temp shot up above 3/4 very quickly driving on level highway roads at 100kmph. A properly functioning fan is necessary in all road conditions - not just some
Pull your old relay apart and see whether the contacts look burnt/charred. Will be obvious if it’s damaged. A more likely cause would be a coolant leak - have you checked all hoses/clamps/heater tap/heater core?