We have always followed the WTM recommendations and schedule, keeping mine together. So even though the mdd is 2 yrs younger than odd, and they are in different levels (one is in rhetoric stage, one is in logic. When odd was first in logic, mdd was still in grammar, etc.) I kept them on the same cycle.
In you case I think I would start over with the cycle just to be simple. That would put modern history year in 9th grade. I would do the civics/government class alongside that the same year, so that it all stays together. Essentially, just do a heavy history load that year, covering your government and modern history all when it makes sense. If you read the WTM history sections it is pretty easy to do.
As far as what to do, I truly find the WTM recommendations simple to follow. It is just an extension of what you do in the grammar stage with SOTW if you were doing all of the extra reading and narrations and notebooking and such as suggested.
For our last modern history year which was in logic stage, we covered state history alongside creating a stage history notebook similar to the WTM style history notebooks. So my kids had a heavy history load that year. They did writing and projects for state history as well as modern American History, and we read original sources, did memory work, created timelines, wrote summaries, read lots of books, went on tons of field trips for state history and documented them for the state history notebook. And now we will just keep those state history books updated throughout high school. We will read state info alongside our ongoing thread of world history as it pertains in time and add to it, plus write and create notebook pages about our state as we explore it and learn about it ongoing. So I wont' have a set aside separate state history period. When we are in say the Civil War, I will have them read a chapter from a state history book on the civil war in our state as we are doing other materials and so forth.
For government, same thing. We will read the for dummies book suggested in WTM on government and original sources as we work our way through modern world/American history year.
In high school, SWB has three texts. One for ancients, one for Medieval World, one for Renaissance World. Then she has suggestions for what to use for modern world history. My high schooler is doing ancients this year. She is reading that text. She is doing the Great Books study and writing about history in context about each particular book she is reading. She is still working through her Geography Coloring Book. She studied for the National Latin exams which goes in depth on Roman History each year and covers mythology and such, so as a family we have done read alouds on a lot of that type of stuff, but her own reading includes the Illiad also. And we watch a lot of documentaries as a family. I will play an episode of Drive Thru History as we eat lunch or the NLEs videos all in Latin that tell about Roman history as if its a Roman TV news reporter. So history isn't a lot different than logic stage work last year.
My logic stager reads the Kingfisher history, outlines from it, adds dates to her timeline, works through her Geography Coloring Book, and writes summaries occasionally on a history or Great Book that she has finished. She watches the videos and studies for the latin exams also. We do a lot of family read alouds. Her book list comes from the Classical House of Learning Literature blog. High shcoler's directly from WTM and WEM.