A coach that throws a punch/slap/aggressive physical contact of any kind toward an opposing coach or player has to be suspended. I'd think at least 2 games at a bare minimum, but no problem with it being through the remainder of the season. That is a bright line that no coach should be allowed to cross without significant penalty.
Gard absolutely needs a suspension as part of the instigation and escalation of the issue. I'd want to give him multiple games as well given his history of promoting thuggery on his team, but that should be addressed by the league separately. The fact that he promotes that kind of play with having probably the dirtiest player in the B1G of the past 10 years whom he praises, and that he is now promoting that same kind of play among the rest of his roster, needs to be cracked down on. Hard.