The way Dave sees it, the only way to fulfill his Gettysburg dream is to pack up the family and move to Pennsylvania, well, he has to get hired first but there's more to it than that. He will have to take a very big pay cut and yes, he will have to convince his wife to pull up roots and move across the country.
Franky, there isn't anything on that list that makes this dream unattainable. However, I can already think of several ways that Dave could feel the excitement of his love of Gettysburg and bring it to life without moving to Pennsylvania.
Orange Road #1: Teach Civil War history with an emphasis on Gettysburg.
Dave is a Civil War expert, there's no doubt about that, he could teach in parks in Northern California where he lives on weekends. Teaching is not limited to a classroom, he could utilize his reenacting skills and contacts to provide intimate history lessons or "story time." On another scale, he could do presentations to middle school history classes and bring Gettysburg to kids the same age he was when the history bug bit him. His passion is so contagious, kids will love him! Heck, everyone will love him!
If Dave were to put pen to paper, write an outline of a creative presentation and reach out to several schools (elementary to college) and service clubs, he would be sharing his passion in a matter of weeks. He may not get paid initially, but he also won't be relocating across the country taking a massive pay cut.
What I can say about bringing your dreams to life is as soon as you start to see other ways to invite them back, you get excited. When that excitement swirls into the atmosphere around you, magic happens! People come into your life who you could never have imagined would appear.