Have you noticed that you reward bad behaviour on his part, especially whining?
said I needed to go to supermarket with him as he was tired of going and the picture wasn’t going to make me rich and I’d been swanning around In spain while he blah blah..’
See in my house if anyone, adult or teen, came out with such a rude accusatory-whingefest, they'd get shot down pretty damn fast and wouldn't get the reward of what they want. Definitely no going to the supermarket together. Definitely no abandoning the only paid work in your household to help him buy emergency loo roll or whatever was so desperate
You obviously let him go on and on at you. No, why should that be allowed? Bloody rude bastard.
We will have to talk about this later. I am busy working now. Repeat ad infinitum.
Don't get into whether it is a good job, will make you rich or whatever. It is the only job anyone has in your household and you happen to love it. Be snippy, be short, cut him off mid sentence. "I am working. I need to get on. I don't have time for this." Or "This is not the right time for this discussion. I am working."
Have tasks set up around you, preparations, cleaning, note checking, that you can pick up and do immediately he starts with his interrupting, whining and attention seeking (not the actual art, you don't want to fuck it up by doing it angry and flustered). The idea is you send the message I AM AT WORK by your actions. He is going on about supermarkets, Spain, how shit you are and how hard his life is. You are bustling about doing work shit. This has the massive bonus that you can
-easily avoid eye contact,
- ask him to repeat himself (useful if he has been rude about your portrait ranking it lower than helping him buy the desperately urgent groceries or such like),
- have long pauses before responding (as you mix, match, check, wipe, etc)
- say "I can't get into this now, I am working." then get on with a thing.
- say "I am not leaving my work now. Maybe later." then get on with a thing.
- or the somewhat inflammatory "I do not want to spend time with you when you are carrying on like this. I am going to continue my work.", followed up by "You have just proved my point. I am not getting into this with you now. I am working."
Or, will result in extreme sabotage no doubt but will feel good in the moment: "Oh FFS, get a bloody job."
I have bad insomnia tonight. Blimming menopause.