I think the core problem in your marriage is that your H undervalues you. As a wife, as a mother, and not incidentally, as an office assistant.
One thing I'd like to suggest. It sounds like you are doing a lot of paperwork for the business. That's good. But you aren't getting paid for it. That's bad. Your H expects you to do this stuff, on top of the child care and the housework. That's fine, its better than you having to find work outside the home. But you are adding value to the business and not getting any credit. Probably not even a "thank you" most of the time.
Many, many couples in your situation have the business pay the wife a salary, or an hourly wage. (Often it is a little inflated vs the work done, just because there are tax advantages to doing so.) I think you should move in this direction, both to help you with your self-worth, and as protection in case your marriage goes south.
You need to log your hours, or maybe record how many items of each type you take care of for the business. Estimate how long it would take you to do each task if you were not interupted by the kids, and multiply that by a reasonable hourly rate. What I'm trying to get at is, how much would your H's business have to pay someone to do what you do? I bet H has no idea how much that's worth. (Just like he has no idea how much he'd have to pay someone to watch his kids 16 hours a day, but that's another story).
You do the bookkeeping--do you have an accountant that checks things, or does the taxes? Check with them about the idea of paying you for your work, and the tax advantages of doing so. Your H might not resist the idea if it was for tax purposes. But it will still give him an idea how much work you really do.
The other way to get this through his head is to take a little "vacation" from the office and just take care of the kids for a week. Let him come home and try to catch up on the paperwork, or hire a "substitute" to do your work. I'm not recommending this approach, but it's tempting isn't it?
