Ideal route -  Kanazawa --> Shirakawago --> Takayama + surrounding area if you like (Gero Onsen, Okuhida, Shintoka Ropeway) --> Toyama ---> Kurobe Alpine Route

For this route, is it really can be completed within 7 days?

All driving?

I dont think I will be going Nagoya, maybe just focus on north area. Checking youtube and it seems most place required either long travel bus or by car. I believe car rental is not cheap as well right?

I am very interest on this part 

Tateyama Alpine route was one way from Dentetsu Toyama Station > Shinano Omachi
Or you just plan until Kurobe Dam only? then back to Dentetsu Toyama Station

I believe your car will be park at Toyama. From Shinano Omachi back to Toyama city by public transport? [If you complete entire Alpine Route]

Most of people I know, after Tateyama Alpine Route, from Shinano Omachi STation to Matsumoto City. From there either go Tokyo / Nagoya.
But you are driving, very interest here