When you had much worse problems and had no issues with 2500 dives that gives a bit hope. But why can I not do diving as a career then as it might heal completely?
I also think you will be able to heal and dive again. Go to that third doctor, a further opinion cannot hurt you.
Your last question instead would require half a book for being answered entirely. This topic was already debated several times here on FB.
Starting a professional diving career is not a "light" decision, it is something which will affect your entire life.
Physical health issues is just a part of the facts to be weighted in.
I was also fascinated by diving, having started at 16 years old. At 20 years I was already an instructor (out of the rules, because at that time, in 1978, you had to be 21 y.old for becoming instructor).
I did teach for some years in a diving club (unpaid, as a volunteer, and also operating as a volunteer in the civil protection agency).
Only in 1985, when I was 26, I started my professional career, working in touristic resorts in Italy and Maldives.
The pro career lasted just 5 years, during which I and my wife (also a diving instructor) did enjoy the best years of our life!
But everything goes to an end. I had started also my academic career at the University, and the wife was pregnant, so we took the decision of giving up, and went back to normal rec diving.
This was also a great fun, teaching our children to swim underwater since 6 months age, and giving them their first air tank in the pool at 2 years, and in the sea at 3 years. The other parents were looking at us as criminals, but our sons did enjoy this immensely, and they grew up as very proficient divers.
Some people continue their life as professional diving instructors for all their life. I know many of them, but as the age grows, these guys become very strange people. At a certain point of their life they see that they cannot anymore switch back to "normal life"; as there are no more jobs for them. So they are stuck becoming old, skinned diving instructors, but loosing many other opportunities which "normal life" provides.
So it is really a big decision to choose scuba diving as your main activity in your life.
I suggest you to evaluate other possibilities than becoming an instructor.
First of all you can choose to become "just" a diving guide, what in the US is called a "dive master". You have no teaching responsibility, and in general you will be doing much better, deeper and more interesting dives than those made by an instructor with novices.
Another possibility is to become a scientific diver, which is what I am now, thanks to my academic career. Of course you need a proper master degree (marine engineering, marine biology, environmental sciences, oceanography, etc.) and possibly also a PhD (which nowadays is highly recommended in any field, as a standard Master Dgree is actually providing a much worst level of knowledge than 40 years ago). In a year you will probably do just 1/10 of the dives a typical dive master is doing, but the number is not everything, better to make less dives but very interesting ones, than to repeat every week the same 12 diving sites with different customers...
Also the wage for a scientist is usually much better (and permanent) than an instructor or a dive master.
See here an Italian research center at Maldives, where I, my wife and our two sons spent a period of time in 2018. Marine scientists are doing their research activity in nice sites like this one:
MaRHE Center
The third option is to become a commercial diver. These are incredibly well paid (compared to instructors, but also to scientists), but the work is hard, at great depths, in muddy cold water, soldering pipes or the like. I discourage you entirely to follow this path. My former instructor did the one-year long training required for becoming a certified commercial diver, then he worked on gas platforms in the Adriatic sea for just one year, and then he gave up and went back to "normal life". It was a terribly had work, 4-5 hours per day in the water with a narghile' (aka as an hookah), scraping away mussels from the legs of the platform. I and my wife went a couple of times helping him in this hard work, so we did experience by first hand how that job of a commercial diver is hard and unsatisfying...
So, factor your current medical problems in the decision, but please take into account also all the other factors affecting your future life before jumping in the world of a professional diving career. My experience is that this is the proper choice for just a very small number of people, and for most humans it is far better to keep scuba diving as a serious hobby, but not relying on it for sustaining you economically.
