OP… It would be most helpful if you could post photos of a closeup of your horse’s head with the Micklem on as you have it configured.
I think then you could receive some more accurate advice on fitting the bridle.
I am even more convinced, having seen the photo you posted, that riding with the bridle as you have described is unwise.
If using the Micklem as it was designed is less than comfortable for your horse, perhaps the Micklem is not the best choice for that horse.
Example: I would love to wear low cut breeches if I could pull them up to my waist, but they are made to be low cut breeches.