To get a "true" resting heart rate you need to record it as soon as you wake up in the morning, even before getting out of bed. Preferably it's done when waking up naturally...an alarm elevates the HR.
A lower resting heart rate doesn't mean you circulate less blood throughout your system - it means you have a higher stroke volume per beat. Your heart is physically larger and stronger, so it can circulate the same volume in less contractions.
If I remember correctly, 220-age to determine MHR is used primarily in sedentary populations and has little relevance to athletes. This formula was derived from a series of tests done in Scandinavia back in the 60's on a cross section of the population there.
RHR is decent indicator of fitness, but VO2 max is better. Anaerobic threshold is another good one, but doesn't have a linear correlation to ones aerobic capacity so it can be misleading.