Oh, my, Allison. I can't tell you what to do. I watched both of my little dogs die, three monts apart, going through the throws of death just like my wife. But, I told myself, "This is what death is." Most things that die go through this, what we call suffering, but I am positive that you are unconscience during this time. The body is just shutting down. So, I didn't do anything but let them die.
Now, in your case, I imagine you will come to this point, and if you wait that long to do it, you must let him go through the process of dying, and that my take hours, as it did in the "puppies" case (I always called them that, even when they were old). That is only respect of the dying process and death. But, if you are in the middle of moving and he starts to die, you will just have to put everything on hold until he is gone, which could take anywhere from two to three hours to overnight.
So, if I were you, I would make up my mind to put him down. You don't have to do it, but if things get too complicated with the move, or it looks like he is taking a turn for the worse, then you can just go through with it. Otherwise, you can just let it be and see what happens. But, taking a stand to follow through with some definite action will ease your mind cause you know you are doing the right thing. It is all in his best interest, and having a plan is always good. You know he will have to pass no matter what.
And, as my father used to say, "Never regret your decisions because that was your decision at that time, and you can't go back."