I’d tackle it.
He is behaving like this because he can - it’s lazy bad behaviour because he’s safe in the relationship, he can’t be bothered to make the effort to make you feel happy. He just dumps on you.
Id say, “your stress is getting worse - I can tell it makes you feel bad. I’d like to help you recognise it and tackle it, firstly because I love you and I hate seeing you getting over-wrought and worn out by the monotony of life.And second because your stress spills over to me because I’m nearby. I don’t want us to end up stuck together in misery! Do you recognise what I’m saying or is this all out of the blue?”
And take him for a long walk in the countryside or a nice woodland or even just a towpath near home, or a bike ride, or a wild swim, or an outdoor yoga session, or a Paddleboarding or kayak session! He needs heaps of fresh air and exercise to reboot his system.
If he refuses to cooperate with diagnosing why he can’t cope and doing something g about fixing why the little irritations are blown out of proportion (maybe a “final straw” if there are big dramas, recent bereavements, financial or health insecurity?) - if he refuses to cooperate in fixing it all then you need to call him out very calmly every time:
”you seems out of sorts, why are you growling at me about pigeons again?”
”are you aware you’re glaring at me? It doesn’t feel very nice to be glared at.”
”I only mentioned the mossy lawn as a fact, I didn’t blame you, I wasn’t hinting you should fix it. I can fix it myself. I should be able to start a conversation and have a reasonable discussion with you. I don’t react angrily when you say you like chips by replying “oh so you’re saying you don’t like my cooking? I can’t be expected to make chips everyday just because you want them.” Think before you speak, and we’ll both be happier.”