Since Luger was so amazing at the time as a heel, was there ever any thought of putting someone else in his place to take on Flair when Sting got injured? To me you could have easily put in Pillman or Muta (obviously getting why the latter didn't happen. Justs aying perfect world and all). Was Luger just a case of being the biggest star they had?

Had streaming been around much sooner, could WCW have survived or was TV a must?

​Yeah, Muta was absolutely in the running to get the spot but he didn't want to turn.  I haven't looked up those Observers in a while, but I think Steve Williams was also a contender, which might have been an OK stopgap. That being said, Luger was definitely the biggest star they had available​ so it's hard to fault them too much for the move.  
And no, streaming would not have saved them.