Having now RTFT I'm beginning to think the DP is a cocklodger.
Look OP, I get that you're upset but your DP doesn't sound great.
Giving in to family pressure 'relatives talking shit' why should he care?
I understand if, for example, they all clubbed together and got the money to send him to the UK, digging into all their savings... but that failed! He had been here for years, he'd have been deported if he hadn't met you. He has not achieved anything through his own hard work. He just got lucky and found a meal ticket.
Despite that, he's still turning his nose up at jobs, 'want somewhere he can progress', not wanting something 'tedious' - he doesn't have much to justify such arrogance.
So many 'tedious' jobs have progression routes. Even say call centre, or waitressing, etc.
What percentage of your problems is caused by relatives pressure? What percentage is caused by actual life issues?
With 2 people on NMW 40K for a couple without children and your disability benefit is not bad. I'm not saying he's condemned to a life of low-earning but your immediate mental health issues blah2 are caused by expectations of a third party that should be put to a stop.
And as a PP said... if his relatives are talking shit, then take it from someone who's been there, even if he earned 100K it would NOT be enough. Not just his immediate family, more will crawl out of the woodwork, pretty soon you will be paying for them all to have cars, new household furniture etc etc while you live like paupers in the UK.
There is a culture of comparing and showing off, 'save face' embarrassment etc etc but you will go down a miserable spiral you can never come back from if you continue to give in.