I view rehoming a dog in a similar way to putting a dog to sleep: better a week too early than a day too late, particularly if you've reached this point.
If there's a breed specific rescue near you, I'd strongly encourage you to use them over Dogs Trust. I wouldn't use any of the 'big rescues' if I was paid (they don't give a lot of good families a chance and hold dogs in kennels for too long, they often then re-home to unsuitable families, they don't feed them a decent quality diet). Or, return to the breeder. A good breeder will take a dog back no matter the age. But please do avoid somewhere where the dog will end up in kennels - no dog deserves that environment.
Not every dog is suitable for every family and not every family is suitable for every dog. And honestly, the only way families cope is by accepting they're doing what is right for the dog.
For what it's worth, I've seen dogs that people have claimed are 'beyond help' thrive and live their best lives in new homes and completely change in terms of temperament. Honestly, for some dogs, being re-home is the best thing that can happen to them and you should focus on that.
Do you mind saying what breed he is, and what the main issues are? Some of it could be adolescence. I don't want to try and influence you or to change your mind if you are 100% sure but sometimes hearing an unbiased opinion can be helpful - if only to have an independent voice say 'no, you're doing the right thing.'