It's hard to work with someone and not be there, but there are some things you can do to help. Grip strength is of great importance so I would suggest purchasing a hand gripper from some place like Wal-Mart. Start out by doing something like 4 sets of 25 reps to increase your strength and endurance. After you can do these with no real effort increase the reps per set. This will also help with trigger control and recoil control. Second I would find an instructor who will work with you in person. They can help you with the snap cap drill you are doing by placing them in a loaded mag where you will not know when they will come up. Your stance can also help, though you didn't mention what stance you use. I prefer the isosceles as it enables you to lock your frame in to help absorb recoil. You will likely get other good tips from the other instructors here, I prefer to work with the shooter to see the small and large things they do that affect their performance.