"to extend 18 months to 3 years, five years, ten"
That is a danger. Obviously I, people posting, don't know your DH ... so we don't know how much of a danger, but it is clear from your posts that you have had had these talks with him before and he is still regarding your dreams as, very much, 'dreams' ... not 'reality'.
That is why I think the compromise has got to have very clear time spans in it. I think that you must be very clear with him why you are compromising (best for all three of you to spend the first year together without being apart for a big chuck of each week, etc), but also very, very clear that you still want to move so part of your compromise is that he agrees that you will both put the house on the market by the time the baby is (say) three months old with a view to having moved, lock-stock-and-barrel, by the time baby is a year old at the latest. I think it would be fair to tell him that is the full extent of your compromise.
Keep remembering that, if he is anything like the vast majority of dads, it is very possible that he is going to be so bowled over with love for his (your) baby when he/she is here, that he is not going to want to be any further away from him/her than is absolutely necessary, and he may well do a complete about face.
You are starting to sound really sad, LIVINGTHEDREAM, and from what you've said your DH is, too. I really do hope that you can both reach some common ground on this and have a chance to enjoy your pregnancy a bit. Your first baby!