Faroutback,
As you look at your son's year and your decision to use MTMM for his freshman year, we want to take care not to switch out so many things and add so much that MTMM actually becomes more difficult and heavy than simply using World Geography for his freshman year. With that in mind, I would lean toward using as much of MTMM as written.
The science in MTMM is actually a pretty good mix of chemistry, physics, and biology with some geology thrown into the mix through the study of fossils. It is a great year of study and quite different than the science the students have just come out of in Rev2Rev. I would encourage your son to use the science in MTMM as written and add either the chemistry 101, biology 101, or physics 101 dvds on his free 5th day - choosing whichever set best suits his fancy. I would leave the sciences in World Geography, World History, and US1 intact for the time when he arrives at those guides. By the time he gets to his senior year, and is likely using US1, we can look more deeply at his interests and plan his science for that year accordingly.
For literature, I would either use DITHR Level 6/7/8 with the 7/8 DITHR Boy set, or he could instead use the boy literature set from World Geography along with DITHR 6/7/8 Student Book (and then the following year do only the BJU lit along with World Geography thus lightening his load for literature for the World Geography year). If you did use the Boy Lit set from World Geography with DITHR, you would just plug each of these books into whatever DITHR genre fits best and teach your way through the DITHR unit with the book. I would stay with WWTB Vol. II as scheduled in MTMM for composition and do the Rod and Staff English as scheduled in MTMM. This combination will give him one full credit in lit/comp.
For Economics, he could either add the Economics study from US2, or he could simply do what is scheduled within MTMM and wait to do Economics until his senior year of high school. Either option would work.
I would plan to add Getting Started with Spanish from the World Geography guide, which you can do without needing the World Geography guide. Simply have him do one lesson a day of Getting Started with Spanish. This will earn him 1/2 credit in Spanish I.
I would leave the rest of MTMM as written. His credits then would be as follows:
1 credit in U.S. History II
1 credit in English (including lit, comp, and grammar)
1 credit in Science with Lab
1/2 credit in Spanish I
1/2 credit in Economics (if you add the study from US2 and 1 full credit if you also do the Farmer's Market)
1 credit in Math (Algebra I or above)
1/2 credit in Bible (up to one full credit if he is also doing Bible reading outside of school time)
1/2 credit in Fine Arts: Drawing from Nature (if he adds additional nature journal entries during the week or during the summer)
Hope this helps! Just for reference, for each year of high school study once he reaches the official high school guides, your son will earn 6 1/2 to 7 credits each year. So, you can see the credits he will be earning through MTMM will be comparable. Most states require between 18-24 credits to graduate with this requirement differing from state to state.
Blessings,
Carrie