This is certainly achievable. You might consider ECE Research Methods in Psychology also, as that is another upper-level exam, and there are IC materials for it. Absolutely use the Excelsior Exam Content Guides and strongly consider using the practice exams. The practice exams give explanations for each of the right and wrong answers after you take them, and I find those VERY helpful. The only exam on your list that I have taken so far is the Civil War and Reconstruction, which I just sat this morning. The IC material was very helpful, and I passed with a 68.

Your one-exam-per-week schedule is not out of line, but you should also consider a broad prep followed by clustered exam approach. For instance, you could take two weeks studying Civil War and Soviet Union, switching back and forth to keep them both "fresh", and then take both exams the same day. You could do the same thing with the Psychology subjects, as they reinforce each other to some degree.

I would strongly recommend finding a test center that offers the online DANTES exams, but that might be just my preference -- I don't like pencil-and-answer-sheet, and I hate waiting for the results.