I am a little confused because I thought that the EPGY enrollment covered 6th grade reading/language arts and either 6th grade or pre-algebra math, so your DS still has two to three years of curriculum left. I realize that it would not take him two to three years to complete that curriculum with homeschooling but it may make more sense to decide on subsequent curriculum after he has mastered the next two to three years worth.
Furthermore, in a b&m school, that stuff covered in EPGY would be no more than half the curriculum. He needs history, science, health, music, art, and computer so the Civil War focus is a great idea. Rather than a canned curriculum, I would use the library and follow his preferences as to sources. Furthermore, with a 3rd grade reading/language arts level and a 4th grade math level, he should be easing into self-directed learning if he hasn't already. In other words, he is ready to feed himself rather than be spoon-fed at this point.
