What do you mean "its gotten so bad I can barely walk him in the saddle"?
I have never met any horse that couldnt walk under saddle. I think itd be best if you have him checked over by professionals before seeking training advice. Maybe he needs a different farrier, chiropractic work, or maybe he has a neurological disorder that is causing this. You need to rule out any possible health related issues before progressing his training.
Is he weaker at some point in his body? Front, backend etc?
Getting mouthy and not listening could be a sign of pain. Your horse is trying to tell you something, you need to listen.
Id be calling my vet. Yesterday.
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