1) It does not have a perpetual calendar. It assumes that each month has 31 days.
2) See this thread among others -
viewtopic.php?f=12&t=338523) The watch is COSC certified which means accuracy from -4 to +6 seconds per day. If the watch is new or recently serviced it may take a few weeks to settle into that. If it's losing more than that then it can be regulated by an AD with a watchmaker.
4) Not wearing the watch at night is no issue, you should provide more than enough power reserve from simple wearing and the watch has a 42 hour reserve when fully wound. If you lay the watch on it's side at night then changing to lay it on its back may cause it to lose slightly less and bring it closer to COSC specs.