Hi! Welcome to YT!!
I have a Dexter, too! Your puppy is definitely a cutie
Every time your puppy starts biting on you make a sound like Couversmom suggested and immediately stop the puppy from continuing to repeat the action. Don't allow him to continue to bite on you & don't keep playing with him when he does bite you hard.
As for the humping, all puppies do that to each other ... I think that it is a dominance thing (for now LOL). I would just correct that behavior and stop him from doing it to you when he tries in a similar fashion as the biting issue.
I know that isn't the greatest advice!!!! I hope it helped in some way.