LR Muzzleloading success

[ATH]

Rig: T/C Omega w/thumbhole stock
Leatherwood in-liner scope 3X9
.25 ACP ignition conversion
installed aluminum pillars, resin
bedding

I opened the season with easy harvests at 60 and 118 yards. I attempted a couple in the 200-250 range, shooting high. I set up a target on my range to check the gun off the bipod. As I was going to go check the target, I spotted a deer standing out on the far ditch. I got under cover and ranged the deer at 375 yards. I scoped my target; the hit was within 1 inch of my aim so the misses weren't the gun.
I decided that I was jerking the trigger (the Omega isn't adjustable and I've had issues with the pull) but that under "range conditions" this was well within my capabilities. The deer was standing right where I set up my 400 yard target, and had lobbed 50+ "kill shots" in a row over the course of the fall.
It was a yearling, but after waiting the doe never returned so I decided to get some venison veal. The wind was calm as I squeezed, but as the gun recoiled I felt a gust and figured it would throw the bullet in front of the deer. When the smoke cleared the deer was gone so I knew I hit.
To make a long story short, the shot wasn't perfect. The deer had been nibbling an itch on its front shoulder when I shot, and the wind pushed the bullet 8 inches forward of aim and into the back of the head through the ears. The deer was standing dazed in the ditch when I arrived with my shotgun and completed it.
I felt bad getting the wind wrong, but how do you deal with variations in the wind at extended range? I assume I'm not the only one to have this problem. I have some drifts calculated on my stock, but if anyone has suggestions for a good ballistic program that would run on a Palm I would be appreciative.