Honestly, I don't have the experience to answer your questions EVO. I tested it and it seemed fine, although when I pulled it off there was a large amount of grease/oil around it and considering the engine has done all of 9000 kms I should've been asking more questions about whether or not it was actually good.
Piston to valve clearance is fine. As I said, I pressurised the cylinders when replacing valve springs, changing the valvespring on the top shouldn't have changed anything in regards to clearances.
As for age of tensioner I don't know. I only recently bought the car. I have ordered a new genuine one from trav which will be here wednesday hopefully, I will reassemble the car then. Hopefully be running by thursday.