My Dad is moving from hospital to a Nursing Home tomorrow. How do I deal with the question "When am I going home"? He has vascular dementia.

“When the doctors say you’re ready”

I agree with ZippyZee and use this "therapeutic fib" with my MIL all the time. It is not immoral or unethical. It keeps their minds calm, which is beneficial for them to thrive where they now live. There is no point in telling them the truth since they will never remember it or come to peace with it. I tell my MIL that when she can perform her ADLs by herself then she can move out (she can't go home since that was foreclosed). She accepts this answer since we aren't saying "no" or "never".

It is recommended that family have less contact initially so that the LO can acclimate to their new surroundings. Have a discussion with admin so you can feel more comfortable with this and feel reassured. May you receive peace in your heart and as smooth a transition as possible.

"You can come home when you get better" or "you can come home when the doctor says you are able to".

No, that day will never come, but he doesn't need to know that.