You did a pretty fair job on the story.

You might try H322 powder. It should do about 100 fps faster than IMR 3031 in a handgun. Hornady and Sierra both list it in the highest velocity column in a 35 Remington Handgun with 180 grain bullets.
From everything I have managed to read the 180 XTP should perform a 35 Remington Handgun velocity. The 180 XTP in my Hornady 7th Edition Manual has the Bullet Performance Range listed at 900 thru 1700 fps. With an initial muzzle velocity of 2000 fps the 180 XTP will be down to 1698 fps at 100 yards. I suspect on behind the shoulder shots through the ribs being over the 1700 fps speed limit will not be an issue at all on shots under 100 yards.

Bob R