Is he a builder OP?
My dh is and we run our business together.
DH is soft as shit, and also works with friends so I have to keep a tight rein on finances, otherwise he would overpay. I also now charge the business for my time doing the admin, as it needs someone to do the admin, and if I wasn't doing it then we would be paying an accountant. Which the business has to be able to afford to be viable.
I insist that it makes at least 10% profit each month. That 10% covers the insurance, any bank fees, any tools or kit. Then the rest is up to DH once I have taken my wage (£100 a week, which is about what we would pay an accountant for the year). He needs to earn a minimum amount each month to equate to what he would earn on his own ticket. Then it's up to him what he pays the lads. As you say, too little and he will lose them. But having consistent, regular work from a reliable employer counts for a lot in this industry.
You can get short term works for more money, but you might only be working 2 weeks at a time, then be off 2 weeks waiting for another start, so we tell the lads it's not top dollar, but we have consistent work, week in, week out for x amount of weeks.
DH loves having his own business. It allows him to earn more as he can make profit on the lads, it allows him a bit more choice on what contracts he takes on, and now we have really worked a proper financial plan, he earns more.
Your DH needs to do the same. Work out what he would earn working for someone else. He should always be earning more than the lads, because you are doing more work and also taking more risk (of not getting paid, tools needing replacing, equipment costs). He doesn't have to rip the lads off, just pay them properly. He also might have to deskill them a bit. We were working and paying for 4 skilled men. When we really looked at it, realistically 3 were doing the skilled work and 1 was labouring. So when one skilled man left, we replaced him with a labourer who costs 50% less. But the same amount of work was going up, it just meant we were maximising in the skills and reducing cost.
You need to sit down and go through the last 12 months bank stats. Work out the flat costs of running the business, then look at the labour costs and make sure DH can take a wage at least equivalent of what he would be paid if he were working for someone else. If the business can't do that, he either makes it pay by changing things or it folds and he gets a job.