Is he alone or does he have another rat buddy? If he's on his own, this is absolutely another reason why he's behaving like this. No matter how closely bonded they are with their humans, it's not enough sadly. Rats need other rats. No question. They get severely depressed, anxious and lonely being lone rats.
Bennett (grumpy pants/formerly bitey pants) will hop up on my lap and take treats now. Theres no way in a million years I would of imagined his doing that in the weeks before and after his neuter!
I pull their cage up to my bed every evening and leave the door open for them all and they can come out and play with me anytime and return to their cage whenever they like. He's got two brothers and no matter how many toys and treats and pettings they get from me on the bed, they never stay out too long really. Some Rats are funny like that, they prefer the comfort and sanctuary of their 'castle'. Their cages are everything to them and they are very attached to their bubble. Their territory, their home, their personal space, safety. They really are the kings of their castles lol!
Don't reach into his cage anymore for now. Wait until he's had the procedure. Talk to him and see if he will take treats etc. I learned that with Bennett before he was neutered and it used to scare and upset me. You will have to wait a couple of weeks (it can vary if I recall) for the hormones to settle down after the operation. Some see an instant improvement. Bennett took a few weeks to show less anxiety.
Sometimes even now, he will gently nip me with his teeth if I reach into the cage, but never enough to hurt me. He's a funny boy. He's grumpy, but when he's in the mood for scritches, boy is he in the mood haha. He also really takes care of his brothers. He grooms them and cuddles up to them and stays close when they are sick. He's very considerate of them and just has the most darling little face. I honestly don't know how I'm going to cope when he passes, I really don't! He's got such a huge personality and he's stolen my heart. It's been worth the effort and the patience to see him happy and living the lovely rattie life he deserves (even though he's a little grump :wink
A biting, hormonal rat is so worth fighting for!