Try to use the "push N pull" firm grip, and dont wrap your finger around the trigger. Use the tip of your finger near the bottom of the trigger.
That was a big part of the reason his groups were low to the right.
That is a huge improvement in both your group size and MPI.
Always, always focus on your front sight and hold the trigger back till the gun comes out of recoil (follow through).
These are the biggest problems most shooters I train have.
As mentioned above, take your time when shooting.
Get good, fast will come later.
AS I mentioned earlier..try shooting 5 round groups, check your target and correct any problems when you shoot your next group. Patch out after each five round group.
This will give you better feedback then shooting 50 rounds at once.
For example, you shoot 5 rounds and it's a nice tight group center of mass. Your next group looks like a shotgun was fired at the target.
Pretty good indication you weren't focusing on your front sight for that group.