What tool could I use to view variable(s) value while game is running?
Debugging is starting to get hard..
If you don't already have it, download FCEUX this emulator has good debugging features. You can view the all of RAM by going into Debug > Hex Editor.
In FCEUX:
Tools > RAM Watch
Can just make a list of memory addresses and watch their values all the time here.
Debug > Debugger
Can place breakpoints on writes or reads to specific memory addresses, and make careful inspections of how they change.
Online documentation:
http://www.fceux.com/web/help/fceux.html