Some of the behaviors you describe are likely to improve after your bun is neutered and his hormones have died down, which will take about 2 weeks. Biting and chewing on things is however normal rabbit behavior, and you should try to bunny proof his area so he doesn’t chew valuable things and/or things that could be harmful for him.
Digging on you is another young rabbit-behavior that isn’t quite easy to interpret. I remove my bun from me and put her back on the floor when she digs on me. Rabbits like to dig, so its good if you can provide him with for ex cheap fleece blankets that he can dig in and bite holes in to his heart’s content.
A male rabbit neuter is a simple and quick procedure. The surgical wounds are small and heal fast. Young males tend to bounce back really quickly.
He should not be fasting when you take him in. Rabbits can’t vomit, so there’s no risk of aspiration and they need to have food in their tummy always for the proper function of the gut.
You should ask the vet about pain relief post surgery -some vets give a long-lasting painkiller and doesnt prescribe a painkiller to give at home – but some sort of post-op pain relief should be given.
The most important thing is that he starts to eat when he comes home- so you can stock up a bit on his favorite vegetables and herbs. Send some of the goodies with him to the vet so he can start eating as soon as he wakes up, if he wants to. In rare cases a neutered male won’t eat and needs to be syringe fed, so its good to have a syringe and some Critical Care or similar on hand. You shouldn’t go to bed on the night of the neuter before you know he has eaten something.
He should be in a small-ish area the first day-days post neuter, and obviously give him a clean litterbox so you can keep track of how much he pees and poops. If he normally drinks water from a bottle, give him a water bowl as well in case he thinks its too much work to drink from the bottle.