You likely have a razor sharp edge on the bottom of your chamber mouth. No amount of extractor tuning will make it really feed smooth and not scratch the heck out of your brass.
The real remedy is to pull the barrel and put a small feed ramp like a 1911 on the bottom of the barrel with a rotary tool and a stone followed by a mirror polish with a Cratex wheel. Of course this is outside the scope of DIY guys unless you have a barrel vise and an action wrench.
After thats done the extractor should be tuned like you talked about and if the timing is right it'll feed nice and smooth.
I have almost ten years behind me working in a Marlin service center and this is VERY common with the newer guns. The pointed bullets in the LE ammo don't help matters either as the lack of a big round nose steepens the angle of the cartridge as it enters the chamber. Whereas a blunt RN bullet helps the round more or less teeter totter into a level position to slide into the chamber.
Good luck
