Background
I'm a 22-year-old and have a long-time partner, who I have been with since we met at university. We both live in the Midwest in the United States, and have been planning to move into an apartment together by year's end. We're in a very good place as a couple and I love the guy to death, and there aren't any problems there. He works a service job at a local retail chain, having started shortly after graduating, and he has worked there ever since to save up money. It's a middling-wage job, but it's better than a lot of alternatives in the area and pays above minimum wage. He's been trying his best to find a better one and scope out other opportunities, but so far not much has panned out for him and the job market in our area is pretty rough, so he told me he would try his best to stay there and deal with it while he looked for something better.
The problem
Over the past few months, I can tell he is getting so stressed and sick of the job that it's affecting his everyday life, and he has grown to hate his job. He tries to bottle it up and not complain, and insists he has no right to complain because at least he's employed at all, but sometimes the dam will break and he'll vent to me about rude customers, last-minute shift switches that ruin his schedule, dealing with people who won't wear masks, etc. I can tell it's getting to him to the point that it's making him upset even outside of work, and when he stays at my place and has to work in the morning I can tell he's holding back frustration about having to go.
On some level, I think he feels like he has to work even if he hates it, and I feel like a contributing factor is that he wants to make sure he can pay his fair share of rent and utilities if we start living together and be a good partner. I really want him to know that it's okay if I end up being the breadwinner for a while if he wants to search for something new. I've been struggling to find and keep work myself this year, and the job I was finally able to nab recently, while decently-paid, is not the one I wanted and it's in a different industry than the one I was hoping to break into. He supported me throughout that process and was a bright spot in my life, and I want to do anything I can to help him with his own career struggles.
My question
I need to know how to talk to him about his job and what kind of support would be most helpful to him, and how to communicate that my support of him doesn't rely on his career. My goals for the conversation would be that he feels better about his career prospects and knows that I want to be there and support him in whatever he decides to do from here.
I could ask if he would be happier if he switched jobs because I don't like seeing him so unhappy, and I would be happy to help him fill out his resume and support him in the process. This feels like pressuring and I don't want to be another person in his life pushing him to think about jobs, since I know from personal experience that is stressful and often unhelpful. Alternatively, I could continue what I've been doing and be a compassionate listener, and try to support him in having the mental energy to keep working at the current job. This feels like it would just continue the unhappiness and that it wouldn't be conveying what I want to convey.
Would some other approach be best? Are there other things I should emphasize? Any help is greatly appreciated.