I think you have the formula right (except for the strength part--pretty sure if you're building muscle mass you're building strength ). High reps/low weight for endurance, low reps (not low sets--typically same number or even more)/high weight for muscle mass.
I can only offer my personal opinion here, but I think it's always wise to give each body part a 48 hour break. But you can split your workouts so you don't have to skip a whole 48 hours of exercise.