On skijoring days go to a different place and teach her to pull in her harness never with her collar. It should work in theory but I've never tried it. A little bad news on the harness. Don't cheat on size or it will only make running more uncomfortable to him. I would highly recommend buying your harness from Rae s Harness shop here in Anchorage.
Booties can help a lot for sore paws, especially when training out of snow season.
Again I would call Rae s Harness shop . If his feet are still a problem they do make a canvas bootie for rescue dogs but they are costly. During winter cloth booties will keep snow balls from getting in his toes and they'll last longer. In addition to booties keep the nails trimmed all the time and keep him off gravel and paved roads as much as possible. Study them and remember what they look like healthy and it will help you know the difference when they are hurt.