Career changes

Hi IMs and IDs,
Hoping to get some advice, and some direction down the right path.
Last night, my husband opened up to me about how he is feeling. I knew something had been off for the last couple of months, but with everything going on I thought he was just going through a stressful time.
We are a young married couple, 2 children, a mortgage, and a one income wage as we are close to having a 3rd surprise baby.
We live week to week, we manage just fine, our mortgage gets paid, food on the table, minimal savings in a separate account for bills and just in case.
The problem is, my husband feels like he is busting his butt and getting nowhere.
He is in a trade that that isn't paid well, but he is damn good at what he does. He is paid a better wage for his trade than anyone else we know, but it is still minimal wage. He is quite depressed about the fact that he can't give us all more (not that I expect it) and he is very much over his trade.
He wants to do something different with more money involved. The one thing he does want to do, is become a mature age apprentice, but to do this we would lose at the least $200 a week. He refuses to put us in that situation, and said he would prefer to continue working and pushing on, than to put us in a bad situation.
I feel helpless, I want to help! When we brought the house, the plan was for me to find work and start paying off the house quickly, but that obviously hasn't gone to plan.
I want him to be happy, I hate seeing him like this, he is a loving father, a great husband and my best friend.
I should include, where we live there isn't a lot of options available, so I am at a loss on what to do.
Any suggestions? Sorry about the long post.