There are very few direct health-benefits to a male bunny. If it’s a bunny with very high sex-drive, neutering him would relieve him from the stress of constantly trying to mate and that could give him a longer life – your bunny doesn’t really seem to have this problem, though.
A neutered male rabbit would for ovipous reasons not get cancer of the testicles, but the risk of that isn’t very high to begin with.

I don’t know how old my first bunny was when I had him neutered – he was an adult when I got him and I had him for a year before he developed a habit of peeing and pooping in the sofa + romantic obsession with my dog, and for those reasons, I decided to have him neutered. The neuter solved both problems. If however your rabbit has peeded and sprayed in your house for 3 years give or take, it may have become a habit and not primarily a sexually driven behavior, and in that case, having him neutered may not stop the pee-marking.

Furniture-chewing is unlikely to be affected by a neuter. This problem can perhaps be lessened by giving him lots of stuff he’s allowed to chew like apple-branches and cardboard-boxes. But some bunnies just like to chew, I have one of those.

I agree that litter-training is a benefit for the owner, but not all owners (or often, parents of owners) are willing to clean up after a bunny all the time, so the bunny may end up sitting in a cage all day long – and in those cases, I would argue that the bunny himself benefits from getting neutered, since it may give him a lot more freedom.

Don’t know if this was of any help at all =/

It really just comes down to how important litter training and stopping the spraying is to you. Neutering is pretty low risk.

Getting him neutered will not change chewing on furniture. That’s not hormonal, it’s dental. Lagamorphs, like rodents, have constantly growing teeth that must be worn down.

Our male Porky isn’t neutered, and did fine with litter training at home. We only have had issues with territorial marking when we had to go to dad’s house during an emergency and Porky was on a yoga mat he felt the need to mark (he stopped when we switched it to a rug from Ikea.) I found the thing that help most with litter training him was meeting him halfway, and putting the litter box where he liked to pee the most.

Another benefit to neutering is it makes bonding much easier. Since rabbits are social animals they are much happier and healthier when they have a bond mate. No matter how much we love our bunnies we are not the same as having another bunny to love.