Marlin levers can be had in cartridges like .444, 45/70, 375 Win, 38/55. These bigger bore guns may be more tolerable for you, and they'll certainly put deer on the ground. Learn how to make the "high shoulder shot". Deer normally drop on the spot.

I can't imagine having an issue while wearing muffs, so you obviously have some real damage. Hopefully you'll find one of these cartridges or another that resolves your problem.