Looks like they're getting along nicely
That's actually the plan for the next one.Oh boy... sounds like he was nervous. They say that there should be no new introductions with rescues until at least 2-3 weeks after they come home to you. They need time to adjust to all the changes... it's unfortunate that you had to take him back.
May I suggest that your next rescue be through an established rescue organization? They can better coach you and provide support so that your next adoption is a successful one.
You are probably right. I would have been much more cautious but his demeanor was so laid back and happy. Other friends and family came over and he was great. My neighbor came over unannounced and I didn't know he was here till he walked into my garage. If I knew he was coming I would have leashed him first so they could meet in a controlled manner. I only know what I was told and what I saw from him in the few days we had him so I would have never expected it. I've only had boxers for the last 20 years and never had anything like this happem before. Other than the occasional puppy playing bite to the ear (messy) I have never had one that ever bit anyone. Lesson learned (measure twice cut once). Next time I will adopt through our local boxer rescue so I'm better educated by them how the dog reacts in situations. Was just trying to do something nice for a boy that needed a loving home.Honestly it sounds like the problem was you let the dog have to much freedom to soon.
In the future, if you try again, keep the new dog crated when your not working with him.
There is no reason for him/she to be out have free run of what ever he/she wants.
There needs to be time for him to adjust to your family. The best place for that to happen is from the safety of a crate