Personally i think 2 litres overfilled is way too much, usually only gtr boys do it due to the extra g forces, and only by 1 litre, however it may have saved your engine. Im pretty sure to fit the rear oil drain you have to pull the head anyway, and to fit an oil pump, you have to pull the timing belt and sump. If it were me , i would use thicker oil only .5 litre overfill, and boot it once, check the catch can, if it is dry, then boot it twice and check again.
There is a lot of debate ver the head drains, but i cant see them making anything worse. I would be pulling the head if the oil doesnt fix it, and doing the restrictors and the drain if you are inclined.