I have a Fairfax headpiece and browband but not the whole bridle on my cob. It was professionally fitted and bought after trying several makes. He has a high crest (gelded late plus breeding), little devil pony ears, and apparently is narrow behind the ears. From the day I got him I'd had...
If you don't feed at the recommended rate he'll be getting a lower amount of vits and mins than hee does from his balancer. I'd stick with what he gets now and add some of a normal mix or nuts if he needs more calories.
If you like him and can get him comfortable enough then I'd seriously consider turning away for a year (monitored of course, I'm not saying abandon him) on a decent sized field with company and seeing how things look then. Mybe look for a retirement livery if you don't have the means to do this...
Have you spoken to your saddle fitter again? It may be that the new flocking has bedded down a bit and he can tweak it a bit to help you without affecting your horse.
Mine is driving bred, big shoulders but also a big active hind end, I did at one point wonder if anything other than harness would fit, be acceptable to him, and stay in place. The answer for him seems to have been an Erreplus with their SL system.
I think you need to find a good fitter that...
Adding to this, if you get the chance and your horses are safe then do stop and chat to people, let their kids fuss them etc. It's a little thing but it can make them see us and our horses as more than just something on the road, and if we're lucky they'll talk to friends and family too. Once...
I've seen many yards with schools I wouldn't be prepared to work a horse in, I don;t se why you should charge less than them. At my current yard plenty of liveries don't use the school so people like that also wouldn't expect a lower rate bcause you don't hav a facility they don'twant anyway.
If you try rubber be sure to feel it and bend it, someare harder than others. Happy Mouth is almost certainly not what you want, it's hard and rigid and if the horse is at all mouthy it quickly develops sharp edges.