I told you that twist had a lot of names! Never heard of the Hamley name for it.
With such a new saddle, I am going to say the broomstick method is going to take LOTS longer to get fenders twisted and soft, than doing the twist and just getting it DONE. I have elderly saddles, ridden often in good condition, that did the stick thing and STILL want to pull my toes inward. This is why I learned about the twisting of fender leathers, because knees didn’t like leg being cranked by the fender. Leather is what it is, and it WANTS to hang straight down, not with stirrup turned for your foot.
I would NOT use Vet Wrap to cover the buckle, it is sticky, probably make things worse on that sore. Not sure if a tack shop could cover the whole buckle with soft leather, latigo?, blunt the edges kind of idea. Covering might make it a bit harder to change lengths, but would pad the horse from buckle edges.
I have put some new covers on my old Blevins buckles, they wore out the original leather. Had to wet the leather, sew the covering piece on wet so it shrunk down tight to stay in place. Not hard, just takes some time.
Not sure if this would help, but in the photo, your fender hangs down some from the tree on the fender strap. Can you push fender part UP, so the fender area is more under the seat jockey flap, letting the strap where you hang the stirrup be longer? You now have stirrup tight to the bottom of fender flap, so maybe lengthening that section, then putting on the hobble strap, will move the buckle lower off his wide part of the ribs. Your stirrup on fender is the same length, but there will be more strap showing from bottom of fender flap to where it goes thru the stirrup top, in that hobble strap area.
Here is a link to how to twist the fender/stirrup. Maybe that will get the buckle forward and away from the horse body.