Hi there! Just wanted to share the app I've built that can help :) I read over 20 books on productivity (including Getting Things Done, Eat That Frog and Willpower) and tried all the methodologies. Then arrived at precisely your results.
So I decided to try to experiment with building my own methodology from the system blocks provided by the books and following the most recent research on cognitive psychology. I ended up combining and simplifying the productivity methodologies, I took away everything that hurts productivity (pretty counter-intuitive, but I removed the concept of "projects") and left everything that matters.
As a result, I explained my way of achieving top productivity in my article: https://medium.com/@nikitakolmogorov/how-i-launched-7-products-in-1-year-efe542b1f8b6 .
I then also launched the todorant.com app (available on web, iOS and Android) which is basically the same thing but automated :)
Hope it helps!