I know a bit of what you are feeling as our horse Alex was injured in a barn fire. His skin was damaged from wither to croup and he remains hairless there to this day. That left us with a 7 yo horse with driving being his most viable career. We worked through things slowly and carefully and today we have a happy and healthy horse who LOVES driving
Actually, Driving Essentials WAS being helpful. You need someone knowledgeable to take a look and determines if your problem is saddle fit or horse injury and where it needs adjusting. Since you are a novice at both the injury and driving, you will be floundering in the dark without hands on help. Without help you can buy Freedman custom made harness and end up with something that doesn’t fit. IOW, it’s not the brand of harness, it’s the special needs of your horse. You have to know what to ask to be changed to meet his needs.
I’d start with the injury. How long have you had the diagnosis of broken withers. Has the vet talked to you about what this means, where exactly is the break, what does this mean for your horse’s ability to move and carry any weight or pressure. Is the horse still healing or are you at the WYSIWYG stage? Once you’ve established your baseline with the horse, you will have a better idea of what he can or can’t handle.
Next, look at the harnesses you have already bought and what your options are. WITH EXPERIENCED HELP, look at the saddles/harness you have… WHAT doesn’t fit, does the treeless saddle have a gullet for the spine? Is it wide enough, enough padding to pad the terret screws? Think of your guy as a Prince and the Pea now… where that saddle might not bother most horses it does bother him. Now look at the DE harness in the same way. Which needs less adjusting to make it what you want?
What worked for us with no bone injuries, but tender skin issues was more of a Gig style (width and padding) treeless saddle
http://www.yorksaddlery.com/images/harness/Gig_Harness_Collar2_Brown.jpg
If you are close to DE, you aren’t far from help either. Check with the My Ladies Manor, Brandywine or other club and ask if someone can give you a hand. Club contacts available on either the Carriage Association (caaonline.com) or American Driving Society (americandrivingsociety.org)