It is always difficult to make a decision to rehome a beloved pet, however, you must do what is right for you, and the mere fact that you came here, to a place where you know that Boxers are well-loved shows that you have both the best interests of your family and your Boxer at heart.
I would love to adopt Thor, unfortunately, I am too far away for it to be feasible for us.
I believe that you are doing the right thing by seeking other Boxer Lovers to rehome him, and support your decision.
You have some time to find the right home for Thor, you don't need to rush.
There may be a local Boxer lover to you that just hasn't crossed your path yet.
I had rescued a coon hound mix several years ago and I was able to use a site called petfinders dot com to place her here in PA, and I still keep in touch with the new parents. She was abandoned near my home, and at the time I did not want to permanently keep her.
We had her for 2 months before we found the right parents for her. We interviewed three sets of parents before placing her. Thor's fate is in your hands, so please take your time with this. It is a hard decision to make, however, you are doing what you see as best for all parties involved.
I wish you the best and hope that someone who truly loves Boxers finds you soon!