I would like to congratulate you first on seeing some improvements.
Regarding "leaky gut" I would be very weary of any doctor who claims you have "leaky gut", firstly regarding this issue it can be tested for although the tests are not 100% accurate they can give some form of idea for example there is the blood test which tests for your levels of zonulin. Zonulin is a protein that modulates the permeability of the tight junctions within the wall of the digestive tract this test is one of the main ones conventional/naturopaths can get an idea if you do indeed have what is known as "leaky gut". I have actually had this blood test done and my levels came back in the normal range and were fine. Although some doctors recommend having this blood test twice on two seperate occasions to have a decisive finding. There is also another test in which i believe you ingest a certain substance and then they test to see the levels in your blood or urine to determine how much is actually "leaking into your system. "Leaky gut" is very uknown and although natropaths claim it to be the answer to most diseases this is all theory and not factually supported. I am just warning you as I wish someone warned me before I began spending thousands and thousands on supplements and crazy diets for nothing and listening to the advice of doctors who were treating me on what they "Thought" I had.
Regarding diets I would also consider any diet that limits certain whole food groups to be careful. Of course cutting out all processed foods and junk food can only overall improve your overall health but when you start cutting out whole food groups i would certainly only do it for limited periods this is through my knowledge of doing crazy diets myself such as the candida diet over long periods. Your body is wired to thrive off a balanced diet of healthy fats, proteins and carbs. Stick to natural foods and you should be fine.
I encourage you to educate yourself very well on this topic I truly believe in some natural medicine and wish you all the best. Please keep the forum updated.
For some tips Find a high quality probiotic which can survive the digestion process (stomach acid) 99% of probiotics are a waste of money its imperative to find a good one. L-glutamine is the mother of supplements for leaky gut start on a low dose and slowly increase your levels over a few weeks. Their is also a product called "restore" personally i tried this a it did absolutely nothing for my symptoms but you can decide if you think it is worth adding to your protocol of supplements.
Best of luck and your so young although the modern western medicine has failed you i can assure you in your twenties your condition will be well controlled the dermatology industry is kicking goals within the inflammatory skin disease area and there a life changing medicine which are now available and dozens more to be approved in the near future.