Agent,
First, let me commend you on being so responsible and loving towards your family. This is obviously an extremely difficult situation and I agree with other posters that you need a neutral therapist/religious counselor, etc.
Only you and your wife can decide what is the best path for your family, but let me share with you a few observations based on watching my husband (who is now in residency in Chicago) and many friends who are now practicing doctors.
I think that at a certain time in your life, usually your 20s, people tend to think that there is one single job that will make them happy. For a minority of people that is true. For most people, it isn't.
I think if you talk to people who are in school/residency most of them will describe medicine as a dream/passion/vocation - but bear in mind that they are incredibly invested in the process (all those sacrifices and it had better be a dream job!) and that they have very little experience outside of the relatively exciting realms of medical school and teaching hospitals. I would suggest talking to doctors who are practicing. The majority of doctors work in private practice, the majority of medical students/residents have very limited exposure to private practice. Personally, I know quite a few happy doctors and quite a few unhappy doctors. Lifestyle tends to be a major reason for the unhappiness as well as boredom in private practice and lower earnings than expected. Make sure you do your research!
Also, on the money issue, I have to say that I think your wife is right regarding your finances across the next fifteen years - - your son's entire childhood. This has been our experience. My husband went to a state school and the average debt burden there was well over 100,000-125,000. Between my husband's loans and my student debt, we have 150,000 in debt and just bought a condo in Chicago (not an inexpensive proposition but since you would be living in the city I think our numbers will be useful to you). I have a very comfortable job. Our joint income is $200,000 per year but will increase when my husband finishes residency. On our 200,000 a year (which let me emphasize is approximately double the starting salary a general practice doctor would make) we live paycheck to paycheck -- we live in a nice, convenient neighborhood in the city, which is expensive but we don't live extravagantly. We are also in a high tax bracket so we only see a little over half of that $200,000. We are frequently stressed about finances. And, we don't have children. If we had children, it would be a struggle. 150,000 worth of debt translates, depending on interest rates, into $2000 per month in payments on a ten year repayment schedule. We are paying the loans now, which most residents can't afford to do, to avoid having my husband's debt grow - - that is collect interest, while its in forebearance/deferment. Then we spend another 3500 on our living expenses (mortgage on a 2 bedroom condo, car, insurance, all household expenses, food etc.), and max out our 401Ks (so we do save alot - - but you really need to save alot or you are going to wind up like alot of doctors I have met who can't afford to retire!). I don't know what we would do if we had a child at this point considering that we would need to save and invest approx. $500 per month to fund a child's college education in 18 years and that we would need to budget at least an extra $500 per month for general costs for the child.
I think given increasing tuition and the fact that no one in the family would be working you should expect at least 125,000-160,000 in loans from medical school. You won't be able to pay this for 3-6 years while you are in residency so it will grow to 140,000 to 170,000 (approx). Very few doctors make 150,000 to start and most primary care providers will never make that much. That 150,000 figure you have seen averages radiologists, cardiologists and specialty surgeons etc. with general practice doctors. Because of your family and lifestyle concerns and your wife's unwillingness to move you would likely end up in pediatrics or internal medicine or family practice or psychiatry. Surgery would be a brutal schedule; opth, radiology, etc. are very difficult to place in and usually require another move, often out of state.
In Chicago, as in most major cities, medical salaries in general are lower than the average. The internal medicine attending doctors at my husband's residency make about 95,000. Even doctors in private practice in internal/peds/family practice would make either under 100,000 or just over it to start. I think your salary would go up if you worked away from the city (e.g. a rural area) or in a state with less HMO penetration.
So, your short-term finances would indeed be brutal. And, by short-term, I mean for about 10-15 years until you pay off those loans. That said, I think as a doctor you do have a lot of job security and across your whole life, this would be a positive financial step. You would ultimately retire more comfortable financially than if you were a teacher, or even a PA or nurse. But, it would come at an enormous cost to your family across those 10-15 years - - basically, your son's childhood.
I agree with other posters that you should look very, very seriously at PA programs. Since your family and lifestyle situation seem to be pushing you in the direction of a primary care schedule anyway, you have more options in terms of what type of health care provider you become. My husband and I talked very seriously about him pursing a physician's assistant or nurse practitioner degree. We didn't choose that path because he was relatively sure he wanted to be a specialist and do procedures (he is interested in cardiology) but if he wanted to be a generalist physician it would have been a great option. Being a PA or NP can have drawbacks in terms of less autonomy and more routine work, but these jobs would allow you to treat diseases, have a good lifestyle, and make enough money now to provide for your family's needs. My understanding is that NP training is longer but they can prescribe and in some state's hang out their own shingle; PA training is shorter but less ability to prescribe without having a doctor in the office. Take a long, hard look at these programs. NPs and PAs see their own patients and prescribe treatments, although usually under a doctor's supervision (which means there is a doctor in the office or within some geographic radius who can be consulted with). Also, PAs and NPs are in high demand - - we have physician friends in Chicago that are having a hard time finding jobs.
A non-MD job in healthcare seems like a wonderful compromise solution for you and your wife. I know other poster's have talked about your wife not supporting your goals, but I do think you have to consider that if the baby is the focus of her life, then your going through medical training is equally non-supportive of her goals. Most of my MD friends are women, but among the male MDs I know, I have seen alot of "medical wives" get totally screwed over - - an absentee spouse, no time together as a family, etc - - not to mention that about 50% of these stay-at-home support system type wives will be divorced by their MD husbands and left struggling financially. Based on my "real world" observations of medical couples, your wife is perhaps extreme in her reaction, but considering her own earning potential and life goals and your financial situation, I don't think she is being irrational.
Good luck!