11 handicap in two years - how can I get better?

Hi all, I've been playing for around two years and have seriously grinded and played an awful lot to get myself down to an 11 handicap.

Progressing from here feels very difficult. I have a baseball grip and a slightly unorthodox swing as I am self taught. Should I look at changing this if I want to improve? Or does the fact that I've played for 2 years and managed to get down to 11 mean that it's working and I should continue?

Also, how much would my game benefit from distance? I hit around 225-240 with the driver and around 180 with a 5 iron, 10 yards apart with each iron. Is extra distance what could help me jump to the single figure level? If so, how can I do this?

Thanks for your help