I have also noticed the many Pyrs up for adoption,the Pyr rescue in my area is full and turning dogs away.I spoke to the owner of the rescue to gather some info and she told me a boat load of what happens why people give them up or abandon them.I will have to say...some will hate me for this...these dogs are bred to Guard livestock,meaning they are normally on large acres and or pastures,lots of room...not saying they can not be house pets but for the most part they need room to run and a job to do.Most of the ones given up according to rescue are bought for apartment dwellers..they get to big and rowdy,some are living in neighborhoods and they are known for being a barker and sub life is not the place for a major barker,a pyr pup is fluffy and adorable and then they grow to be large size and no longer wanted or have room.These are all the things that the rescue had told me.
IMO they are counrty dweller dogs,they need room to run,a job to do to keep them happy to the standard of there breed(what they are bred for)lots of people have great success making them calm house dogs so not knocking that at all..BUT for the most part they need acres to run/Guard on(job to do).Dailey walks on a leash IMO is not enough for a dog of this breeding in adolecent years..maybe when they are older and more settled..even then I think they need room.
Any one getting a dog should consider living conditions,do i live in a crowded neighborhood.. do i get a breed thats a well known barker by bred standard alone..do i live in an apartment..wil l it be crowded and he in the way when he is grown..IMO you get the bred that best suites your lifestyle/living arrangmets for both you and the dog to be really happy.
So IMO part of your problem is not a bad miles,its what I just described above.BUT you love miles and want to keep him so you will have to make the best of it and try and work with him on certain issues,You have to be commended though for not just getting rid of him ,you are willing to do what it takes..thats a great doggy owner.