Grunch: Very briefly...

#1 Fold River (you already know that)
#2 Fine
#3 Turn bet won't protect your hand as the pot is so big. Your stuck calling to the end like you did.
#4 You HAVE to bet the turn here. You have top pair, top kick and the nut flush draw vs four opponents in a relatively small pot. You CANNOT give anyone a card cheaper than full price. Who knows, someone with a gut shot might even fold.