Alright, you definetly need the shock collar.....When he runs deer, give him a nice, hard blast of the thing....He should get the message then, if he does it again then give him a harder blast of it...Make him learn what he's doing wrong the hard way....If it doesn't work he's hopeless....
As for the squirrel, he might not like it....Different hunting dogs hunt different things...I've had some that I tried on bear but wouldn't run but now they love to run coyotes...
Try and have a little patience with him, but don;t give him much. If you only want a squirrel dog, get rid of him if he won't hunt them...
But, some young dogs do need patience, like some of my 1 year old bear hounds need to be broke from whining to be let out when I have my dogs getting a bear going....
Dogs act differently, just find out what's best foir your dog.