Sounds fairly normal to me, plecos are generally nocturnal and don't like light. I've had one that behaved similarly. If your plants are real then he'll be eating them at night so don't worry about him not eating during the day. Even so, he'll scrounge anything left over he can find to eat at night if they're fake plants.
Their armour plating makes them very resilient to attack from other fish, just see the odd nipped fin.
The one to watch will be your rtcxtsn as they can eat plecs whole, although it's more likely to go for your other fish first, especially your bala sharks. How big is that tsnxrtc? how big is thet tank? and is there plenty of hiding places like a big tangle of bog wood for the pleco to avoid it in?
