I don't know about Norwegian Forest Cats, but I have had a large number of cats spayed or neutered that roam our streets. For what it is worth -- a regular housecat mixture usually fully matures in the second year, but does not achieve full growth for some months after that. I neuter them at 9 months unless they show a tendency to mount everything in sight (males, females, grown cats, kittens, etc.) or display possible testosterone-driven behavior like bitting other cats, picking fights all the time...
Before I assume this last cue to neutering, I check that the male is not suffering from blocked kidneys or gut (crystals in the urine, blockage from furballs, internal abnormalities -- any one of which would give pain and discomfort, which, in turn, brings on bad temper and aggressiveness...), spinal injuries, a recent wound that is "hidden" beneath the fur (they usually show up when they get infected and some part of the cat starts to suddenly swell), a near-death experience from a dog or stone-throwing kids, or simple human problems like arthritis, sprains, etc.
Once that is out of the way, I would proceed to neutering.
Cats do punish owners for things that really annoy them. One minute they are loving and the next, they remember that they are angry and will lash out. However, his biting may be exaggerated love bites -- displays of the deepest affection -- a sign that you turn him on. Sometimes you can train the cat out of this behavior. You can be very still when he bites down, gently stroke him around the head, ears, throat, etc. without trying to extricate the part of you that is being bitten (this takes fortitude and patience). If he is also using claws, gently stroking between the pads of the offending feet will usually make him relax his hold. After he is completely relaxed, you can use your other hand (if the first one is in his teeth) to stroke his cheeks and along the edges of his mouth until his jaw relaxes. Then VERY carefully you can withdraw your hand or, if he is latched onto your ankle or arm, you can gradually and gently place a hand between his mouth/claws and that part of you, still talking soothingly all the while.
If this seems to work, it is probably less testosterone and more behavioral -- at least for now. If he persists in the behavior, try picking him up firmly and quickly by the nap of the neck and depositing him into the nearest room with a door you can close on him. I call this quiet time, and usually say, simultaneously with my action "OK, let's have some quiet tme." The words "quiet time" are notorious with my cats, and the longer they live with me, the quicker they react -- very often by stopping whatever they are doing that is offensive, and then they become coy and even embarrassed with themselves and apologetic.
Everyone has to work out their own patterns of control according to the needs and personality of their individual cats. So you have to find the path to your own cat's psychological make-up.
If you want to continue breeding your cat for a while, try some of these other methods. If you get a second cat, I'm with the advice to get him a Norwegian Forest female and be sure they can't escape you house. Otherwise you will have a lot of mixed kittens as well as purebred, and most kennel or cat registries will not issue papers to any litter where there are also mixed-blood offspring. If you are not seriously in the business of breeding, then neuter your male when you have had enough of letting him breed. I have successful had the total termperament of males as old as 6 or 7 years changed within a few months of neutering. It does help, even when the full male behavior patterns are very well ingrained.
Testosterone is the villain, in cats as well as in humans! A little ensures the species, but an abundance fuels violence and even irrationality.