If you use the shield block reaction to successfully block all damage (the damage was less than the shield's hardness), would any special abilities such as a Wight's Drain Life be blocked also?
On paper, no. There's nothing in the rules stating that directly. You should see with your GM, as there are some abilities that it would be logical to cancel by blocking all damage (like poison, typically).
I think it's on the special ability description.
I have seen some saying "if you hit and deal damage" and some other saying "If you hit" ( without the "deal damage" part ).
Not sure neither if it's an oversight or not, nor what to do with generic ones when nothing is mentioned ).
As for the wight, it does have to apply damage
When the wight damages+
Further damage dealt by the wraith increases the amount of drain by 1 on a failed save to a maximum of drained 4
Thanks. I think I'll just rule it as 'no damage, no hit'