no the fuse is just to protect the mains cable from melting in case there is a short circuit in the pump, the pump will draw what current it needs!
as for the noise, dunno :-/.
you can't push the tubing in too far, so it wouldn't be that.
have you turned it off for a bit to see if any bubbles come out the top? you could try that.
i think you can unclip the front plastic cover, without taking the tube out of the inlet, so you should stay dry providing you're not too boistrous! try doing that to see if anything's loose underneath. don't worry, all there is under there is the impeller housing, it's completely watertight.
that's all i can think of right now, sorry.
good luck!