As others have said, it's a common age for things to change. He's not refusing, he's just altered his patterns, from the sound of things.
He's still feeding overnight, but not so much during the day, is that right?
It could be there's a specific reason for not wanting those day feeds, which will right itself with time - ie, teeth, or whatever. (All the things you mentioned could be contributing).

Supply-wise, you'll keep making what he takes and if he needs more, he'll ask for more. Your supply at this stage will be robust, it will bounce back if it flags, all it will take is more feeding (baby willing). The left-right imbalance is a bit of a nuisance, but it's quite possible to make enough on one side only, so from a feeding perspective it doesn't matter. (You might not like the look of it, which I quite understand. Feeding more from the smaller side is the way to try and rebalance that, but you'll have to convince the little guy.)

Now, the most important question: How is he? If he's growing and thriving and still doing normal poos and weeing, then he's probably fine. Always go back to your child - how is he, is he doing ok? Changes in patterns and behaviour are not always very good indicators of what's going on. Now, if he's actually showing signs of dehydration, or you have other concerns with his health or wellbeing, then he might need encouraging to take more milk and/or a medical consult.

If you want him to take more milk, give him less food/water (particularly water). Breastfed babies don't actually need water, they can get all the fluid they need from milk, so if he's thirsty and nothing else is on offer, he may ask for more milk. Generally, though, if he's fine and doing well, you may be ok to just continue as you are. Let him decide when he wants a feed.

If you'd like to encourage more day feeds, try different settings, the bath is an old standard. Make it nice and comfy, make the breast available, but don't try to feed him. Make it about spending nice time with your breasts, without any pressure to feed. He might surprise you. When babies are refusing, or you're having issues to get them to feed well, then any nice interaction with the breast is a positive. If he's happy to just be there with your breasts, that's good. If he nuzzles, licks or has a bit of a latch, then comes off without feeding, that's good. It's all headed in the right direction.

You're doing fine