@Mrs.K,
First, thanks for filling in some of the blanks so we know a little more about what's going on and why you're not happy. You are there and we are not, but I think we get an overall view of the situation.
Second, sorry people replied to each other and not to you. For some reason that seems to be happening a lot lately. I'd recommend you just ignore it, but that's only my suggestion, not a requirement or anything. Take it with a grain of salt.
Third, speaking of "grains of salt" I want you to know that even though you've presented your side as clearly and factually as possible, I am aware that there is another side to the story and that most likely his side is quite different than your side. That's only because it's human nature to make oneself "look good" whilst making the spouse "look bad" (super general, generic terms there)...and that's okay. I know it exists and so part of me is trying to bear in mind what your husband's side might be as well.
Fourth, to answer your questions, I have been divorced but it wasn't after 16 years of being a SAHM. I had two elementary-aged children when my first husband cheated on me and refused to stop cheating. We owned our own business together, but I worked around the kids...so I walked them to school, then came into the office and did administration and bookkeeping until 3pm...walked them home and did some work while they did homework at the kitchen table...made dinner and got them in bed...then worked some more from 9pm to noon. I was out of the workforce and self-employed for about 10 years, and my exH made roughly $6k/mo while I made $2k/mo.
When we divorced, my exH "took off" to be with his mistress (as in, moved to another state), and without him the business could not run, so I was with no way to provide for myself and the kids. Like you, I have an autoimmune disease (RA), so it wasn't as if my options were limitless...BUT I have skills that are very marketable: bookkeeping, administrative assistant, business office manager, and LOTS of computer skill. So when we divorced, I didn't ask for alimony. I figured I was fairly able-bodied and would find a job and provide even if it was poorer than we had been. If I had asked for it, I believe the prevailing ruling was a certain amount per month for a certain number of years in order for you to get training/get on your own feet--then you're own provision is up to you. So for example, the judge would consider that my exH would likely still be able to earn $6k/mo compared to my ability to earn $2k/mo and say that he should pay $1.5k/mo for 4 years so that he'd average at $4.5k/mo and I'd average $3.5k/mo for the amount of time it might take me to go back to college and get some degree or training that would result in better employment chance for me. THEN, after the 4 years, it would be reviewed...because he might still only be able to earn $6k but I'd be able to earn $4k now... Make sense?
BUT I DID ASK FOR CHILD SUPPORT!! Now, my thought there was that he made the kids with me, and it was fair and reasonable for him to do his share financially to care for the kids. It was back in the 90's but he paid about $800/kid I believe, and what I did (so he'd know what it was used for) was that I put that money straight to the house payment. That way, I wasn't frittering it and he knew the money was literally putting a roof over the kids' heads. Next, we did agree to split costs 50/50 but you know how kids are: "Mom, I need a baseball mit" "Mom, we have a field trip tomorrow and it cost $10" "Mom, it's time to join the football team and sign up costs $XXX" etc. All those nickles and dimes drove my exH CRAZY so I agree for him to pay the entry fee for sports (one son did football...the other baseball) and equipment, or entry fee for something like "drama club" or those kinds of clubs... and I would do all the nickel and dime field trips, "I need ___ by tomorrow!" and drama club costumes. In the end, it was roughly equal, and it was a way that he felt like he could "plan for it" and I was okay being more flexible.
Lastly I'll mention this: prior to my divorce, we lived in a 4000 sqft dream house with a large yard and in-ground swimming pool. We both had 2 year old cars, and honestly we were rich. Because he chose to continue cheating, the kids and I had to move from your upper-middleclass home and sell it, and that was sad. But we found a cute little townhome near their school (closer to their friends) with a community pool, and we could afford it, AND it was OURS so we never felt powerless again. It couldn't be taken from us or used as a threat in any way. So my guess is that if you do choose to separate/divorce, you will very likely have a change in your life circumstances. You may not get to keep the house and get alimony and "have the exact same lifestyle"...but you know what? That's okay! Maybe you and your children will have to move and sell your current house, but wherever you go, look together and choose it together so that your new place has all the little things each one of you finds necessary. You may not have the same financial blessings that you have now, but you know what? That's okay! Love is free and making cheap dinners together is free and having your kids' friends over without hubby complaining about it is free...a very happy, good life can be had for no cost! You may not be able to just buy what you want, when you want, but you know what? That's okay! Learning to save is a good lesson. Postponing gratification is a good lesson. Learning the value of an item is a good lesson. It's all okay!
Hope this helps you to maybe envision what it might be like...