Mmmmm I have tried these methods before and to a huge extent it does work outrunning the run,
but I would think carefully before trying it! If you think he is running agains't the bit then letting him bolt is going to serve as good practice for bolting. Practice makes perfect! If his tongue is sore or his bars are damaged I would look at changing his bit to a half moon straight bar which I believe is extremely soft or even better no bit at all if possible. Try not to punish his fear with a harsh bit :( It sounds like he's not had kind hands until he met you and this sort of damage can take years to reverse or delete....put your heart back in your hands and then carry on handling him...something I would try is downward transitions and half halts....lots and lots and lots and lots and lots until you start to hear and see the lip smacking and mouthing (signs that he is ready to learn) from your pony and then try upward transitions followed by downward transitions eg...from walk to trot to walk...do lots before moving up a step from trot to extended trot to trot...lots and lots and so on to trot to canter to trot. The first steps may be boring but they are the foundations for your pony to understand what is expected...give him a chance to learn it before plunging headlong into a canter/gallop.......Bravo for taking on this little man!! There should be more people like you in the world!