Hi, I'm mainly a lurker (thanks for all of the helpful information!). I thought I would respond about the fitbit and sleep - I unfortunately have more experience than I would like because my 8 year old has sleep apnea.
My sleep doctor would say anything over 10 wakeups is something to check out. The problem is not just the awake time but the disruption to the sleep cycle. My guy will wake up 15-30 times with the fitbit but if you put him in a "real" sleep study, this will translate to 75-100+ because they monitor much more closely there. The ultimate result is REM sleep in the low teens when it should be in the mid 20s for his age group. This can impact memory, health, growth, everything really. To give an idea, his younger siblings are all below 10 when they wear the same device. Also, he has absolutely no idea he is waking up - his pulse oxygen drops and he wakes to breathe and goes right back to sleep. The only way I knew was that he seemed more irritable during allergy season (when the apnea is at its worst for him) and I noticed his bed looked like an elephant slept in it. We had already had tonsils and adenoids removed when he was younger due to clear obstructive sleep apea.
If you wake more than 10x and you feel tired, I would check it. Other signs of sleep disruption can be a messy bed, snoring (we didn't have after the tonsils were removed), dry mouth (from mouth breathing).
The difference between a good and bad night's sleep is truly amazing for my son. You really can't believe the difference!