The clues and the suspects(underlined):

#1-Jim comes in late. He has a black eye. Toby comes in 5minutes later. He has a swollen right hand.

#2-Jim walks by the xerox machine, where Pam is standing. He pats her ass
"Dwight. I mean Jim." She shouts.
#3-Michael tells Pam that she will have to stay late. She smiles and whispers"yes!"
#4-When at Pratt, Pam attends a concert with Alex. She gushes about how great of a time she had, Guess she hadn't heard that the concert was cancelled!
#5-Ryan brings a video to work and shows it. It shows the little bastard fucking an unsuspecting Pam

I own none of this.