How old is this puppy? What is his breeding?
Do not muzzle him. Search this site, there are several tricks and methods for thwarting nipping. Yelp. Anticipate the nip and get a toy in his mouth BEFORE he bites. Don't play with your hands. Time outs. Chew toys.
Jumping. Ditto, search the site for methods to discourage this behaviour.
Neither jumping nor play biting have anything to do with testosterone. They are not sexually dimorphic behaviours. They are simply normal puppy behaviours. Please, please do not count on neutering to magically correct behaviour problems, you have to correct these behaviours now, yourself.
Are you taking him to training classes? A trainer will show YOU how to teach him to behave himself. Puppy classes are just the start, though since I have no idea how old he is, maybe he is too young for more than that right now.
He sounds like a lovely, friendly puppy who needs nothing more than his loving owner to teach him how to control himself and keep his exuberance in check.