It'll be interesting to see what he replies. He may see it as you controlling him or putting pressure on. I suppose it depends on how you worded it as well. Did you make it appear that you were doing it for him or did you say ' I would like to do some things for myself and that means you swapping places with me in the house?'
Maybe a month was too long? I doubt he can think a month ahead. If he doesn't respond to your email, do not ask him about it as that may be seen as pressure and pursuit.
I only have adult children so cannot in anyway relate to what you guys have to contend with. When my H first left, I refused to let him take the dog to his 'love pad' and in fact really limited his access to her. Now I say, 'I'm away all day Saturday so the dog needs sorting out please' I give him plenty of warning, but it is for my benefit alone and to help me GAL.
I, in no way wish to imply that my dog situation means that I understand yours, or that it's comparable, and I don't really care whether he has a relationship with the dog going forward; but I do feel it's a step forward for me; It has reminded him that he has some responsibilities and enabled me to GAL.