Thank you for taking this bunny in!
A mature male bunny should have scrotal sacs ie testicles. A rabbit can suction them up into the belly though for example when he’s feeling stressed, so the absence of visible testicles is not a sure sign the rabbit is neutered.
If he’s been eating veggies and not a lot of pellets, he’s probably got enough water from the greens. Rabbits on a diet with lots of fresh greens barely drink at all.
As for digging and scratching it could be about stress relief (getting a new home is stressful even if it’s a change from a bad situation to a much better one). Rabbits have a proneness to digging. It’s not a sign of anything being wrong. You can give him a cheap fleece blanket to dig and burrow in, it’s often highly appreciated by the bunny, but the blanket will never be quite itself again, so don’t give him anything you really like.
As for nudging/nipping you he probably did want you to move your hand. Nudges and nips can mean “Pet me” or “A treat, perchance?” Or just “You’re in my way, move”. Rabbits as a rule use their nose and mouth and teeth to communicate with us. Aggressive biting tends to be rather unmistakable and often accompanied by growling and/or boxing.
It seems like he’s trying to communicate with you, and that rather means he’s accepting you. If he didn’t like you I doubt he’d try to “speak”with you.