I suggest you post here a picture of your film leader after you cut it. With plastic reels I had problems until I understood I made two mistakes in cutting (shaping) the leader to insert in the reel. Plastic reels want the film to advance, for its entire length, inside the spiral. The cut must be straight, and the corners must be well rounded, not clipped at 45. The leader is the head of the "train" and it goes along the narrower bend inside the reel. If not properly cut it will resist advancement. After I learned to properly cut the leader my loading become very fast and trouble-free. I use Jobo series 1500 reels.

Also, I don't know if you use the trick of inserting the leader inside the reel while still in daylight. You then insert reel and film inside the changing bag, with all the rest (scissors, tank, tank lid etc.) and close the bag. Then you insert your hands inside the bag slowly and gently "looking" for the reel, and begin loading the film. I would never manage to put the leader inside the reel while operating inside the changing bag. It's much easier if you do this worst part in daylight.

Finally, you could build a sort of "cage" with "iron thread" (I don't know if that's the correct term in English. I think you get what I mean) and put this cage inside the changing bag. That would keep the bag away from the hands and make for a bigger air volume inside (less heat and less concentration of humidity).

As an alternative you could buy a "changing tent" instead of a "changing bag". The former are bigger and have a frame inside to keep them in "inflated" shape.

Regarding the sacrificial roll, the obvious suggestion would be to practice with it in the changing bag, not only in daylight.

Hope this helps
Fabrizio