Yes you can hunt deer with that set-up but it is not reccomemded due to the tight constrictions of the choke and the possibility of deformation when the slug passes through it causing excess pressure. yes you can hunt squirrels with that set-up but you will have to remove a few bb from the carcass if you intend to eat. I would reccomend buying a new barrel for deer hunting of any kind.
"Si vis pacem, para bellum". If you want peace, Prepare for war!!!!