I'd march down to the local dealer and pay top dollar for a new tensioner before I reused the old one.
I have used quite a few timing belt kits from ECS in the past, including the first time I did my timing belt. No car I've done a timing belt on had any issues with the tensioner from the ECS kit. I put 85,000 miles on the one I used. That said, I never paid much attention to the brand so I can't remember where it was made. I just know they included parts from OE suppliers and that has always been good enough for me. They could have changed to a cheaper alternative recently in their kit.
Lately I have been using TB kits from Europa Parts because they allow more selection and choices of brands for each part. The INA tensioner is supposed to be very good quality and the same supplier to VW just without the logos on it. The INA is about $80 I believe.
I'd recommend adding the motor mount hardware and coolant. Also recommend only replacing the camshaft seal and crankshaft seal if yours are currently leaking oil. Buy them if you're not sure you'll need them or not. You will not need the single crankshaft bolt (M16x54) if you do not replace the crankshaft seal.
You're more likely to cause damage when using an impact. Use hand tools and make sure the bit is fully seated in the hole. Lightly tap it in and keep the bit pointed straight while turning.
You should replace the 6 crank pulley bolts, so no need to worry if you have to drill them out. Buy a $20 corded electric drill from Harbor Freight along with a cheap set of metal drill bits just in case they're needed. The bolts are soft because they're stretch bolts. Drilling is quick and easy.