This is a screenshot of my Task Manager when I had nothing open and before I started up I:SS.
This is a screenshot of my Task Manager when I'm in-game.
I used the snipping tool because the Fn + Prt Scr wasn't working
So your computer is definitely not hitting any bottlenecks. You are running all these 32 bit programs, is there by chance a way to run I:SS in 64 bit? (i don't know myself, don't run it that often, and have never bothered to try to tweak it).