Wonder if coolant pump impeller spinning freely means the shaft & impeller are turning properly or is the impeller spinning free on the shaft so it doesn't turn? Suggest starting up with the radiator cap off, full of water, look for movement. If no movement, then pump is bad or some passage is <really> blocked.
I had the same problem, replaced the radiator with a new one from partzilla and now the bike is so cool my fans barely ever kick on now. I know it might sound like a simplistic response but sometimes radiators just won't cool anymore. If you don't want to spend the cash, you can try a coolant flush first. But the leak is a concern... Do an in depth inspection of the radiator to ensure no leaks or cracks.