One sentence in your post got me thinking. Reread this first:
"BTW we are praying about it, but worry that we both want things so badly that we are unable to clearly decide what the answer to that prayer might be!"
Remember that you may WANT something and your husband may WANT something, but as soon as you started a family, your WANTS came second to your family's and your household NEEDS. You WANT to stay home, but if your family NEEDS food on the table and clothes on their backs (and a roof over their head that doesn't belong to someone else), you might not get what you WANT. The same thing goes for your husband. He may WANT to be a chiropractor, but his family NEEDS may not allow him to have that right now. And I'm not just talking about financial needs. His children need to have their father around to share their precious childhood moments. Once they are grown, you can't relive those moments.
There's no rule that says he has to do the program as quickly as possible or right away, right? Maybe he should take the classes slowly. This way, if he discovers that it's not what he thought it would be, you're family's not up to its eyeballs in debt for a career he's not going to have.
$150,000 is a LOT of student loan debt. I got out of college with about $20,000 in debt, which adds up to about $200 a month in repayments for the next 10 years. Imagine what your repayments would be if you had 7 times that much debt!! By the time you've repaid your husband's soon to accumulate student loan debt, you'll be ready to take on your own kids' college loan debt. He should consider paying as he goes rather than getting into that much debt. Yikes!