A little confused. I went through some of your older posts, so I think I understand??? The 'big guy' is your latest addition, right? And you've been having problems with his aggression for quite a while?
If he's the newest one, and if the other two are getting along and have made a home with you then maybe you would be correct in finding him a home where he could be top dog, and not have to compete with other doggies . . . We had a dog who was like that; actually we found her wandering around the park. Took her home, put fliers up, and tried to find her owners. To no avail; we were going to just let her stay (even took her to the vet and got her shots since we weren't sure if she'd been vaccinated) , but she was too aggressive with the other animals. She was very sweet with humans, but was not at all socialized with other dogs -- finally my husband found someone at work who didn't have any other animals and wanted a dog and could provide a good home for her.
Hope this helps
Jess, Rhapsody, and Tiger