While I admire the effort to improve by practicing a lot, you must also make an effort to avoid reinforcing bad habits. If you want to shoot well, it is worthwhile to have someone teach you. It takes less than a hundred repetitions to form a habit, it takes thousands to break one.
Find a local club that teaches marksmanship fundamentals.
Read books or military field manuals that are intended to tech people how to shoot.
Attend an Appleseed where the volunteers spend a weekend teaching you how to shoot.
Take a training class at a facility that caters to the customer experience.
Don't obsess over your zero. Just circle your group with a marker and adjust so the point of aim is roughly in the middle. I don't think a deer is going to wait around to see if the statistical center of a large number of shots is where it should be.
As you eliminate one bad habit at a time, the position and shape of your groups will change. Learn the relationship between the clicks on your sights and the number of inches on the target, then adjust as often as you need.
And focus your eye on the front sight.