Due to my lack of knowledge of islam and Ramadan at age of 13

At very young age of 13 I had very bad company at school, college and university the colleagues I had company with were talking to me about pornography and that I am the devil and will go to hell. I started masturbating during Ramadan and did ghusl and had no knowledge that it was a great sin. I know now. I am now 40 my health does not allow to me fast as I suffer with back pain, high blood pressure and enlarged prostrate. I regular pay kaffarah for missed fasts. Will allah forgive me and I am feeling very scared in returning to him as I admit my sins and regrets about it. What can I do to stay on right path as a muslim. I read quran, pray 5 times a day and have done ummrah several times allahmudlliah