Thank you for the clarification! Your been in Canada makes things easier with the range of foods you can get for him.
With the diet (seeds and human food) and the light schedule (sleeping 10 hours a night) he has had for the last five years, he cannot be anything but overly hormonal and, although I think his aggression is mostly due to it, I still think that the fact that your partner has been absent for weeks and your change in the routines he was used to had also a lot to do with his biting you.
Fruits are not that high in carbs when you consider the amount of water and fiber they have, that's why the best indicator is not so much the number of calories of any food but its glycemic index. But, in any case, parrots were meant to eat fruits and they metabolize fructose (the source of carbs in them) much better than we do so, unless we are talking about a fruit that is super high in sugar which should not be given every day, they are fine for them.... at least, that has been my personal experience with parrots because none of mine are overweight.
I am not sure if you were asking me or exactly what you were referring to but if your question is about the 'strict' solar schedule, yes, it needs to be strict and that means full exposure to dawn and dusk without any artificial lights and sleep when night falls naturally. It's the only way you can keep them from producing sexual hormones off-season because we can't do the food or weather that nature also uses as triggers to start or stop production. I also like to use a good quality full spectrum light for during the daylight hours because it helps them produce the happy and reward hormones (which put them in a good mood
).
Personally, I suggest you consider putting him on a strict solar schedule because even when your partner comes back, making the bird happy by it, if you don't, he will continue to produce sexual hormones and suffer chronic pain in the process. An animal in pain is an animal that, sooner or later, will become unpredictable... they can't help it.
I also suggest you consider changing his diet because, unless you are providing him with avian vitamins in his water or sprinkled on his food regularly or exposing him regularly to direct sunlight and making sure he is eating a LARGE range of produce, he is going to develop nutritional deficiencies.
As to switching him to a better diet, cold turkey is not going to work. Parrots are not instinctual eaters so your leaving food he does not identify as food in his bowl expecting him to realize this is, indeed, food is not recommended because it doesn't work. Parrots are highly altricial birds that need to learn what is food and what is not from their parents, they are not adventurous at all when it comes to food, they only eat what they are used to eating so it takes a long time to convince an adult bird that something that he has never tried before is good to eat. Besides, birds all have a very fast metabolism and need to eat twice a day... they can go without food for a number of days but, eventually, you will have to give him his seeds or he will starve to death. Easy does it with them and persistence, as well as experimentation on the way or where the food is presented is key but what works the best is for you to take the high protein food out of his cage after he eats his dinner and goes to sleep and, in the morning, about one hour after dawn, eat breakfast with him (HIS breakfast, not yours). Fruits usually work best and, for grays, I have found that juicy ones are a favorite. Try watermelon, cantaloupe or apples (they all seem to like those) and, for veggies, try fresh corn on the cob lightly steamed (I don't know of a single bird that having tried it has not made it its favorite). I feed all my parrots gloop (and they all came to me eating something else and were transitioned to it without a problem) and raw produce for breakfast and a good quality seed/nut mix for dinner (my grays get mostly nuts and very little seed). If you are interested, there are several recipes of it (and other stuff) in the diet section.
Mind you, none of these things are going to work immediately. It takes months for an out-of-whack endocrine system to go back on track and, even when they stop producing sexual hormones, they still have them in their bloodstream but this is actually a great time of the year to start a solar schedule when you have an overly hormonal parrot because the days are still long (as they are used to) but they are getting shorter naturally (which is what makes them stop producing sexual hormones).
Ah, one more thing, I don't know if this is so for all males but, in my personal experience, the ones that make a nest when alone are females, males only do it when they have a female.
As to interacting with him now, I would spend as much time with him as I could trying my best to reproduce the same exact routine he used to have when your partner was home but, for now, I would use a stick to move him from one place to the other instead of my hand (you don't want him to get used to biting you). I would not use gloves... I know that lots of people say they work but, in my personal experience, parrots hate them.