Makes no difference unless you're "aiming" some way such as point of aim. I've always shot split fingers useing a boot tongue tab. Pick one and stay with it. Your "instincts " will sort it out if you shoot enough. Takes alot of practice to stay proficient in trad archery. More time than I can devote these days I'm afraid. So after 45 years of longbows, selfbows, and recurve, I bought a compound this summer. Don't feel like bowhunting to me, but I get to get in the woods 3 days from now.

A couple observations. First off judging by the Amazon arrows you say are 28” long you really are only drawing 23-24” at the most so probably only 40#, which is still plenty. Your arrows being 400 spine are way, way too stiff plus if you are using 100 grain points they act even stiffer. Best advice is to get weaker spined arrows such as size 600’s or 500’s. Or you can use heavier grain field points like 200 grains which will weaken the spine.

It appears to me that your brace height may be too low. On those Black Hunters you should be at least 7.5”-8” max. That measurement is taken from the throat of the grip to the string. Twisting up the string will increase the brace height which should help with arrow flight.

Those Black Hunters are cut past center so with no shelf and sight window material on it and the carbon arrows with a low brace height may be causing most of your problems. I’ve had to build out the sight window of my Black Hunters to get better arrow flight. Building out the sight window like you did looks like it helped but looks like you may have gone too far.

R U closing your left eye when shooting? Most people shooting without sights use both eyes open.

If the nocks on the Eastons are too loose just pinch them together some, that should help.

The strings that come new with the Black Hunters are notoriously not very good and might be something you will want to change at a latter date.