Just my two-cents, Maria.
First, I'd like to pass along what a trainer friend of mine who trains Dutch shepherds for K-9 work says about using the word "dominant:: she refrains from using the word dominant because too often it is used (even by trainers) to mask problems that don't have anything to do with dominance.
For instance, a fearful dog might very well appear to you as dominant when really they just don't know what is being expected and there's been inconsistancies in handling. Fear-aggression is not "dominant." True, you may not know the dog's past, but you need(ed) a consistant and knowledgeable game plan--for any dog.
Secondly, akitas are a tough breed. I know a shelter who hates to see them come in: if they're there, they probably already have problems on top of being a tough breed. Double whammie--and not for the feint of heart.
You felt like you were doing the dog a favor. But I have to concur with others right now that the dog needs professional help--not a cookie-cutter trainer or someone who thinks the answer is to prong the dog for a year. It honestly sounds like you are in over your head--and good for you for looking for help on this forum. Please know that you are not being attacked, but rather, people are looking out for the dog's welfare--and yours, too!
What you may not know is that RESPECT helps serve you to establish the alpha position with any dog...and consistancy...and fairness...and patience, especially with a rescue. Physical confrontations DO NOT help establish respect.
What would you think and how would you behave if you had to be around someone everyday whose reactions could never be trusted, where you never knew what you should be doing? One minute, something is okay...next not-so-much. Think on that for a minute, but make no mistake: thinking that dogs think like we do is a mistake.
You need to learn how dogs think and, like Aaron posts with the photo of Danke: work WITH the dog.
I hope that you make some wise decisions. You've been given some excellent advice here by LB members. Please digest it all and do what is best for both of you.
Sincerely, I wish both of you a wonderful outcome. But you need to get things straight right now before more damage is done.
Oh--and one more thing: I may have missed the nuiance in the post about mouthing--but mouthing is a dog's natural way of correcting. Be it you or another dog. It can escalate. It should never be encouraged.
You don't see "dominant" dogs getting mouthed by subordinates, unless it's an accepted submissive gesture.
I only adopt probematic dogs: my current DS is aggressive and was a bad mouther. It took time and patience, but he doesn't mouth anymore. Respect.