1) Again you're ignoring that he won UCL, not only UEFA cup with Porto. No one is looking for Poch to take over some big club, right?He won the Europa league though with a Porto side just like Mourinho however no one is looking for him to take over here are they?
Every decent manager like who? At the end of the day he's doing a great job for Spurs competing with teams like in no other league. If he was the manger of Bayern Munich or PSG i'm sure he would have titles to his name.
Did Benfica spend money like Porto at the time? Not gone back to confirm but i wouldn't be surprised if Mourinho was yet again in charge of the club with the most funds (Porto had a good business model and still do). I'm not taking nothing away from Mourinho by the way his track record is incredible.
2) Spalleti, Ranieri, Jardim, Emeri etc. Good but not elite managers. He is doing a good job, but has stagnated and should have won something so far (be it the title on Leicester season, or FA Cup last season). I don't remember a single manager who won nothing on his first decade and then later started winning a lot. It just doesn't happen, in fact most of achievements happen on the first decade.
3) I have no idea if they spent more than Benfica or not, but I know that they didn't make big signings. And for sure, there were multiple European clubs who spent much more than them.