Judging from the pictures something looks a little off, but I'm not an expert and it's been ages since I've ridden.
Here are some tips that a writer named Shawn shared on another site. I hope this helps!
"The best way to determine if your saddle fits your horse is to place the saddle on his back with nothing between your animal and the saddle except an old, flat sheet. Any type of padding distorts the fit, filling in hollows and covering up areas that may rub or be too tight.
To ensure the saddle is in the right spot on your horseís back, take one finger and place it on the button on the side of the pommel. Take your other finger and place it just under the cantle at the top of the back panel. When your two fingers make a straight line, the saddle is in the correct spot.
Move behind your horse. In a correctly fitting saddle, you should be able to see all the way through the gullet from your horseís rump to his withers. If you arenít seeing that, the saddle is too wide for your horse and is probably sitting on his spine.
Check the pommel. You should be able to place three to four of your fingers sideways into the gullet space between your horse and the underside of the pommel. A too-wide saddle sits further down on the withers and wonít allow this check.
Move to your horseís sides and slide a hand between the saddle flap and the animalís shoulder. In a well-fitting saddle, your entire hand should slide easily without pinching. Check both sides of your horse to make sure the flaps fit evenly. A too-narrow saddle that squeezes your hand can damage your mountís shoulder muscles and withers, and cause back soreness.
Confirm that the back panels of your saddle donít rest on your horseís hips or rump. A correctly-fitted saddle will sit squarely on the back, between the withers and flanks."