hey fabi. like suggested, the only thing i think you could do is try and find the smallest pullies you can to replace both the tensioner and the one under the TB. that alone will help free up some space. also try and see if you can fit a smaller belt. maybe a 1/2 - 1" smaller if the tensioner allows you to. i dont remember how much "swing" your tensioner has. that would stop the tensioner from "pushing" the belt so far down if you understand what im saying.... it would make that pully sit higher causing the belt not to touch the water pump. get it?
if that doesnt work then your next best bet would be to just not use the pully under the TB at all. completely bypass that one. Obviously this would require a significantly smaller belt. id guess 2" smaller or so... i personally did try that on my setup and it kinda worked. but my tensioner (LS tensioner on water pump) wasnt pushing on the belt hard enough which caused it to slip under load plus its kind of a long distanse between the tensioner and alti which allowed it to flop. BUT with how yours is setup, i wouldnt think you would have that kinda issue as long as the belt was the right size.
i think that route or the smaller pullies will solve your problems.

