The throw everything at the wall and see what sticks system of engine diagnosis and repair can be troublesome, you'll never be sure what you fixed or what new problems you caused vs, old ones returning.
This has been a common theme for many years if not decades, the engine randomly stops and no one knows why. What you need is DATA. I have both a fuel pressure gauge and a fuel filter vacuum gauge and have solved issues that would take 100 years to find otherwise. Moyer even has a kit specifically for this issue:
https://moyermarine.com/product/the-...m-ktas_01_564/
You certainly can plumb in a system with an electrical and mechanical fuel pump. I would not do it aircraft style with the pumps in series, if the diaphragm starts leaking into the crankcase and you hit the electric pump switch it will be bad
