Will upload an improved pattern.
I think it is not necessary to decrease in the rib section of the thumb - 16 stitches on a US2.75/ 3 mm needle seem tight enough.
Moreover, I would suggest that after the thumb gusset the pattern should be repeated one time more than the pattern says, especially if you like your mitts to cover your knuckles.
Mail me if you need to clarify something, the new pdf will be available shortly (21-22 Dec).