Mouth is great! ears accurate. Eye sufficiently large, but need more shading to tell more. bridle details
Bit too low in mouth ,. menaing mouth is too "short". Mouth is as long as the distance from edge of ear to eye. and the bit is then on the far inside of the mouth, so raise the bit about 20% higher.
Jaw is a wee bit too small. The overall shape of the pony's head is rather longish and lacking in a large jowl, like a qH would have, but your drawing is a bit TOO long and needs a tiney bit more jowl.
Overall, really getting close to accurate. I am very impressed on how much you have improved in the 6 months Ive been seeing your draw. Wish we could sit down over tea and draw together!