The instructions say to cut the tab off, but (my understanding of) this was the one I've marked with a red X below, turned out i needed that tab so welded it back on after, and powdercoated.
For the TTS covers you can get a length of o-ring locally;
Looks like you've a more up-to-date pulley than mine, although it looks the same just with a flanged collar around it. How is that collar fitted? can you slide/press it outward so the inside part (that you bolt to the front cover) is slightly proud?
Didn't think there was space between the belt and the engine front cover for that flange but,,
If you didn't get a pin spanner or have a suitable one e.g. for angle grinder, you can put a jack underneath the tensioner too to turn it up