Perhaps the $100 ATM was to pay cash for the Best Western, originally held by cc. The $5.00 charge may be for a movie or a phone call that wasn't on the original bill. You can call the motel and ask what the charge is for. (I could tell you not to snoop, but that ship has sailed.)
I think S2 would have said "we sleep in car" not "papa sleep in car" if they had both really done so. I think "papa sleep in car--other bed too big" was H's excuse to S2 when S2 woke up alone and H was nearby but not in the room. This could have been at the motel or somewhere else.
For reference, I always let my X know if I am taking my boys out of town, even for part of the day. It is not a violation of H's privacy, it is common courtesy to the other parent. I think that at minimum, you need to get an itinerary from H next time he takes S2. Preferably not overnight. (It would be reasonable for you to require that he explain this weekend before allowing him to take him again, but not sure that's DBing.)
Check with the family court or whoever in your state--they probably have guidelines for age-appropriate visitation schedules, maybe even posted online. Younger kids are more likely to visit all-day or only one night, possibly every Saturday, vs older kids who visit on alternating weekends for 2 nights.
