I think that the neutering came at the same time as adolescent testosterone rush. He'll be feeling sexually frustrated It will go on for the next 6-8 weeks.
Rabbit behaviour is to be "social climbers" - to get up as far as the social ladder as they can - & they'll be aggressive to climb the ladder. They are also very sensitive to our feelings.
It's not uncommon for them to include people in their social heirarchy, & play the physical & psychological game of "Let's you & me fight it out for top buck". Some get aggressive over space (living quarters) or food, which is easier to handle. The important thing is not to even feel frightened, (= he's achieved the beginning of back off). I found it equally important not to use any aggression eg squirting with a water spray was advised - he bit the nozzel!! & won by eliciting an aggressive reponse from me. I managed to find a way to hide my inner annoyance too.
I used several methods with my buck simultaneously. He'd growl & paw the air (aggressive display) when I opened his hutch. I wore thick gardening gloves - complete protection - no fear & importantly no back off.
Some people do a loud EEK sound when they bite. As it had no effect with us I asserted my dominance "top rabbit" by forcing a rabbit submission from him = you're boss. I put my index finger across his forehead just in front of his ears & increased the pressure until his chin was on the ground. He was very reluctant to give that last millimeter which confirmed to me that we had dominance issues.
It sounds crackers but to hide my annoyance I sang silly happy songs. Can't feel cross while doing that.
The digging & biting the cushion is a typical rabbit temper tantrum. Mine is allowed to have a strop on the cushion in his carrier.
With spraying - that can be reduced by not using any scents in the house.
Because mine couldn't be neutered I got him a toy rabbit to hump, but I don't recommend this in your situation. As the hormones die down we want him to forget about humping, not get in the habit of it.
If he was being a pain in the neck, & repeatedly challenging he was put in his own pad where he couldn't do much damage. They can be naughty on purpose out of boredom just to wind us up & get a chase or some action. The important thing here is plenty of distraction/play with short breaks for us in their own pad. Again no pay off of a chase - drop thin towel over them pick em up & out.
It's a combination of standard rabbit behaviour & the human child in the terrible 2's.
Within 3 weeks, Thumper still had his strong personality. He's never layed a tooth on me or anyone else in 4 years, he's incredibly affectionate, we have a very close relationship, he's still got his plums, & he's as good as gold.
