Lets try to logically approach this dilemma of yours. If SLS's are bad, then so are preservatives in foods (including baby foods) and hair dyes many more 'products' that we tend to use on a day to day basis(FYI SLS are also in body washes and soaps). Every chemical has its pro and cons. Every chemical is a foreign substance to the body and the body will have its way of removing it or fighting against. Despite all preservatives we still continue to eat preserved foods and use hair colours and body washes... then why make shampoos with SLS the only villain. You will find lots of information on the side effects but it is information that you personally will have to assess and then come to a conclusion on if you want to use it or not. SLS based shampoos are harsh , meaning they make the hair and scalp dry. If you want me to be honest, since shampoos are used as short contact therapy, I feel the harm that they cause isn't something that you need to fear so much that you stop using shampoos. As to your second question, there is no best shampoo for treating dandruff. You should ideally visit an allopathic dermatologist and get yourself examined. About your hair loss... looking at your tablets you need to start modifying lifestyle and simultaneously start on a dermatologists treatment. There is no easy or quick fix or single shot therapy for hair problems. Have a look at this article: http://www.skinmatra.com/single-post/2016/11/10/Hair-Woes-10-Things-You-Should-Know-About-Hair
Next Steps
Here is another article that might interest you: http://www.skinmatra.com/single-post/2016/11/19/Male-Pattern-Hair-Loss-Genetic-Or-Heredity
Health Tips
Avoid too much of net surfing. I believe it is not the information that is important...but HOW YOU INTERPRATE this information that matters. Else this world would be full of online educated doctors and rocket scientist.