Dogs are amazingly resilient when it comes to rehoming them. They will grieve, stop eating, and will show symptoms of melancholy. They will, eventually come out of it and will start to feel better. It WILL be a big change and it will take some time for both of you to adjust.
I think that the move will be harder on you than it will be on him. If this will secure your future, you would be loathe to let the opportunity slip by you.
I don't think that he will forget about you. We place rescue dogs in new homes and I visit them from time to time. They still remember me and still love me. But keep in mind that he will fall in love with his caretaker as well. She will become his support and will win his affection.
Let me know if you still have concerns.