Hey
I also have a physically demanding job! Insanity has helped my body immensely and I feel much better at work. I am more flexible and stronger, I also have a lot of stamina, energy, and endurance that I didn't have as much of before.
I think a few days off for being sick is fine, just start up with week 4 again

You're probably ready for the challenge of month 2 anyways! Exciting!
If you aren't doing your workouts, just don't add in the exercise calories, since you won't be burning any

Andrew