Nitpicking and overly criticising others can be a way to try and regain control, especially when other things are spiraling. Anxiety and general restlessness is a terrible trigger of mine for acting like this, because I know I can't do much about the actual thing that's causing me stress, so I become a horror for everything else (cleaning, others' harmless habits, signs of weakness in people, noise, bad manners, etc.) Small offenders on their own, or just non-issues, but they become a nightmare to me if I'm anxious or overstimulated.
My advice is choosing a calm, preferably solitary moment to reflect on what's bothering you about him, actual problems that he can fix but doesn't, or just personal quirks that you didn't mind much before? If things aren't that big a deal when you're not in close proximity, you might try and find a way to unsee/unhear it until this phase is over.
For stuff like noise, visual annoyance etc. from others, I just find it easier to remove myself from the situation. Watching something engaging, earplugs, earphones, changing rooms, listening to something that you like, gaming... The point is directing your attention away from the point of irritation so it fades into the background. When your mind stops fixating on it, your tension will diminish too.
If there are some things that you genuinely think he needs to work at, choosing a less rocky time to discuss them is probably better. He must feel on edge now, αs are you. The important thing is you are aware of this and trying to find a solution. I don't know if this was helpful but good luck!