The first rule is to not say "always" or "never", because you can find exceptions to every rule
. However, most of your conclusions are good general rules.
I would make the following counterpoints:
- Trousers could be light colored or even white if they are made of a washable fabric
- Trousers could have front suspender buttons either singly or in pairs
- Fly-front trousers are not just OK, but pretty well universal style by the 1860's
- Caps can be worn as well as hats
- Men's overshirts may be tucked or untucked. If you think about it, it's pretty difficult to tuck in a shirt that's worn over your suspenders...