You sit up very straight (good!) but it looks like you may post really big. Also work on bending your elbow... You look like you are trying too hard. Your arm goes from completely straight to 90% straight in all those pics (and similar in first post)
I envy your posture lol
I would say your biggest weaknesses are arm position and that you seem to be ahead of him.
He makes a lovely English horse and looks happier lol. He seems to like the bit (how does he feel?) and looks to be relaxed and forward and moving into the bit whereas before he looked to be sucking back and like the bit was too much.
There's no reason you couldn't use that bit for western also. The curb gives him the "headset" but true collection is so much more and I prefer the way he looks in the more recent pictures and is a step forward towards true collection.
Thank you for the critique, yes my trainer said my weakest thing is arm position I am working on that, and he feels relaxed and happy its just a simple snaffle, I had a lesson today and am seeing a major improvement and he's starting to get his headset in a more natural way (: I will keep this forum updated (: