If you are in America, you can apply (now that the closing date has been extended) via your state's healthcare clearing house. You can start with www.healthcare.gov and go from there. You can also buy short term insurance from an association or group you are a member i.e ieee.org and others.
If you are outside the US, you can buy it directly from insurance companies.
You did not say if you are leaving a job with insurance - if that is the case, you can use healthcare.gov when you leave.
I am not sure how the laws are now, but you can structure your company so healthcare is a benefit for everyone. You will probably need a small salary to make it all work out. Definitely a question for your accountant.
I just completed a late in life PhD (a few months ago), so this is my reasoning and experience. I wish I had completed a PhD a lot earlier in my life. It is a great experience - the depth of research is unlike any commercial research job I have had in the past.
I am not sure you can look at it entirely as a financial transaction: I do this PhD and then I get a certain financial return. You do not know the job market in 3 to 5 years or if your research will be in demand. You have to do it because you really like the topic and want to become an expert (or be on your way to expert status).
If your goal is basically financial, look for company sponsorship or PhDs in countries other than America. It is much cheaper overseas and most students receive a job which covers expenses. Keep the opportunity costs low.
An MS degree from a good school, in a hot topic, will be much better than a PhD from a low ranked school or an unpopular topic.
I have noticed that the students who do well in their career post PhD select their supervisor and topic based on what is in demand. Other students work on what they love - and maybe do not have as lucrative a career. But maybe they do not care about money.
In the end, you will be more valuable. You have to decide if the cost benefit analysis works for you. There are a lot of forums where PhD students discuss their frustrations and goals. Just do a search and start looking at them.
To get an idea of the life of a PhD student, and to meet some current students, attend research seminars (most are now virtual) at the school and topic of interest. See what you think and ask the students what they think. Good Luck!
There are numerous paths for going back to school. A big question is cash - Will you have enough to pay for school and take care of other obligations in your life (do you have a family? Mortgage, etc)?
Learning is always good - you just have to pick the method/path that works for you. You also must keep your expectations inline with your abilities and method of schooling you pick.
Unless you go to a very good school or you want the full-time campus experience, you might be better off going part time. At 30, you will not be part of the regular social scene - so you can gain most of the experience in a part time program. If you live near a large city (New York, Boston, Washington DC, etc) there are very good schools that have programs aimed at you. The hours are arranged for people with full-time jobs.
In your 10 years of work you have learned how to manage your time. You are also much more motivated than you were when you were 18. Studying and homework are easy compared to work.
If your company will reimburse tuition, you can afford the better quality, higher cost university. Unless you have high hopes (move into research) just about any reputable school will be fine as you stated your goal is to learn and change the direction of your career. Not having a BS is a handicap.
I highly recommend going back to school. Look at the programs close to your location and weigh the benefits/costs of part time vs fill time. Will the cash cost of going full-time be recouped by a much higher salary? If you are serious, you can finish in 4 years if you take classes in the summer, test out of everything you can and take distance learning classes. Maybe less than 4 years if your classes transfer.
It will be a lifestyle change - can you handle going to class 2-3 nights a week? Read and study on the weekends?
Get some information and get started. Even if you think there needs to be some changes in scheduling at work, I bet you could do one course a semester.
BTW - I went back and got my BS in CS after 5 years - then an MS part time and finally a PhD. If you enjoy the material - it can be done.
Startups are getting more support in Europe. There are a number of good accelerators: Techstars has affiliates in Europe. Startupbootcamp is creating a network of Accelerators in Denmark, Ireland, Spain and others. Hackfwd is mentioned in another post. I work with LeCamping.org in Paris.
European governments see that startups create jobs. France (believe it or not) has a whole range of support services and cash for innovative startups.
It is still harder to form a company, open a bank account and get going. In America it takes a credit card and an hour. In France and England it takes more time and effort.
Another believe it or not - salaries for engineers are lower in France than America. Education is great and there are a large number of people that want to work for a startup.
There is no Palo Alto of Europe - Yet. Many locations are trying to win that race. Overall there are many opportunities.
Sorry to hear about your predicament. Good to see that you are addressing it directly.
Are you in Paris? There are a number of groups you can work with to get assistance and bounce ideas. La Cantine is a great starting point - a group of French tech entrepreneurs that adopt a more pro-active approach.
I am a mentor at Le Camping www.lecamping.org and would be happy to discuss some ideas and introduce you to other people that may be able to help.
I understand that you do not want to put too much detail on the forum. Contact me at jhlewisjr the usual gmail. I will be meeting with some companies tomorrow and Wednesday and could meet with you either of those days.
If you are outside the US, you can buy it directly from insurance companies. You did not say if you are leaving a job with insurance - if that is the case, you can use healthcare.gov when you leave.
I am not sure how the laws are now, but you can structure your company so healthcare is a benefit for everyone. You will probably need a small salary to make it all work out. Definitely a question for your accountant.
Good luck on your company!