Those stab jacks are just too far back, I completely agree. Tough to tell from the pics you have but it also looks like you have half assed spare tire mount under the very back too like mine did.
Here's what I would do. Remove both stab jacks, order a new one to replace the damaged one. Back the rear tires onto a string and string the line up to the bottom of the rear bumper. Remount the jacks far enough forward that they do no stick below the string line and they will never get drug again. My Puma Unleashed has the power rear jacks and they are mounted MUCH further forward. The spare also needs relocated elsewhere or it will drag too, mine is now between the rear axle and stab jacks. I've elected not to add casters to the back of mine as of yet, since removing the spare (gaining about 7" of clearance) dragging hasn't been an issue.
Looking at one more thing, it looks like you have tons of clearance between the truck bed and trailer. Does the trailer ride level? Hard to tell in the pic, but if it doesn't lower your hitch or raise your pin box and that will help keep the back off the ground too.
My Puma has the same "bumper". It is super thin and only boxed right behind the taillights. I can't remember if it was channel or just angle, don't have the trailer here right now. It should not be a big deal to bend it back and make it look acceptable.
2013 F350 dually
2015 Palomino Puma 351THSS Premier Edition
2015 Nights camped 15
2016 Nights camped 5