Western saddles aren't made for jumping horses. Their shape and weight distribution is not designed for jumping obstacles. The issue you are having with your horse sounds like either a saddle fit issue, a foreword (mental state, not speed) issue with the horse, or an issue with the rider's seat. Leg pressures should be the same in both english and western. The amount of leg pressure you apply is based on the horse, not the discipline. If you really want to start jumping your horse, I reccomend you go to a saddle fitter for advice. Also, I DON'T reccomend jumping bareback when you are a beginner. That will cause you to clamp on the horse, and most likely slam on the horse's back.