I'm quoting the following because of how incredibly spot on every point is.
@Art2doc , read it. Then read it again. Every point here is something you
NEED to understand when making this decision. These are things every applicant should consider before applying, but they are especially true for those who have children relying on their success as you do.
For my 20 cents (my opinion is too long for just 2 cents here, sorry) as a (semi-) non-trad who is now finishing up med school with an SO who has been with me 5+ years...
Your current relationship as you describe it is not conducive to being successful in medical school. I'll refrain from giving any professional opinions about your spouses' problems or situation, but from the picture you've painted I feel confident in saying that this relationship would have almost 0% chance of surviving medical school (not to mention residency which is typically even more stressful and time-consuming), and if you did decide to enter medical school in your current situation, I think your chances of getting through would be greatly decreased.
Everyone talks about the stress medical school and residency puts on future physicians, but it's rarely mentioned how much pressure and commitment is required from physician spouses. Spouses need to understand that they are a second priority to medical training, when kids are involved the spouse becomes a tertiary priority. It sounds like your husband already struggles with this, and entering medical school with this situation will only hurt both of you as well as your children. If you two stay together and you pursue medical school, you NEED to have these relationship issues worked out. To add to what Instatewaiter said, I've seen many good relationships fall apart because of medical school, and know of exactly zero relationships that weren't at least "good" that survived medical school. That's not even counting residency. So if you choose to pursue medical school, you need to either make sure your husband is completely on board and providing far more support than he currently is or end the relationship. Not saying what you should do, but I believe entering medical school in your current situation would likely have devastating results.
Now, let's say you decide to end the relationship and pursue medical school (not saying you should or should not do this, just giving my perspective on this hypothetical), there are still going to be many obstacles. In addition to the previously mentioned age-related struggles you'd face, you may very well have to move multiple times to places you've never lived and may not know anyone. If you end up in medical school in another state where you're alone, what will the situation with your kids be like? Will they come with you? If so, will you be able to find a babysitter/support? Or will you sacrifice your own study time and "make it work"? Will their dad fight for custody? Will there be legal issues if you moved away? Etc. Keep in mind, you may not just be moving once, it may be multiple times. You may have to move for medical school. If you go to certain schools (mostly DO), you may have to move again 3rd year when clinical rotations start. You may have to do an audition rotation somewhere and not be home for a month. If that happened who would take care of your children? You may have to move again for residency. That's potentially 3 separate moves in a 4 year period. Are you okay with moving your children around that much? Some people are okay with that. Personally, I wouldn't be.
Then there will be residency, which will be a minimum 3 more years, possibly 6-7 if you pursued something competitive or did fellowships. So from med school to attending would take minimum 7, up to 11 years of your life. That's 7-11 years where you're missing out on major points in your children's lives. Yes, there will be plenty of time to spend with them, but there will also be times when you desperately want to be there for them but won't be able to (missing games/recitals, not being there to help with boy/girl problems, being so tired you can barely function as an individual let alone as a parent, etc). Can you accept that? Earlier I talked about the sacrifices made and support given by spouses, but you should also be aware that some of those will be required to be made by your children as well. So you have to ask yourself if it's worth it.
There are also many unforeseeable/unexpected events that could happen. What if someone gets in an accident or becomes really sick? What if the divorce gets legally messy or there are legal issues with custody (still working under the assumption of you being single here)? What if you fail boards or don't match? What if you get partway through medical school/residency and hate what you're doing? What if something happens to your step-dad and he can't afford to pay your tuition anymore? These are things that most students don't have to deal with or just find a way to deal with if they occur. However, for someone like yourself who is in a unique situation and isn't "most students", any one of these events would likely be far more difficult to handle. So they're just things to keep in mind.
I'm not trying to discourage you from pursuing this path or be overly negative, though I'm sure that's probably how this post is coming across. I'm just a realist, so I think it's important that people have a solid understanding of what they're getting themselves into and some of the hurdles they will/may face in the process. This is especially true for someone entering medical school or pursuing medicine who already has a family with children.
So to summarize in a few points:
If you do decide to pursue medical school, you need to have your relationship situation worked out
before you begin. You need to understand that you will be making many sacrifices in terms of your ability to be there for your family, and your family needs to understand that they will be making sacrifices as well. You need to understand that this path will require those around you to be flexible, and will likely require you to be flexible as well (especially given the current situation you've described). Finally, you need to understand that if you pursue this route then you have to commit to it 100%. You can't be constantly distracted with a million other things all the time. Yes, sometimes things will happen and we have to deal with them first and put med school aside temporarily. However, those events have to be the exception, not the norm. If you weigh all these things and still choose to pursue medicine, then go all in and don't look back. If you chose a different route, I don't think any reasonable person would blame you. Either way, I wish you the best of luck in whatever endeavor you decide to pursue and hope everything works out for you regardless of the path you take.