A bit of fruit is probably fine. But certainly not much. A few dried meal worms are okay too. But I would be very carefull eith chicks and treats. My advice was for adult chickens.I think strawberries would be fine. Any kine fruit really. Mom will help introduce them to any new foods. Banana is one of my favorite foods to feed any of my animals.
I wonder if he is scolding them for wandering too far. I'm sure Shad has got some great thoughts on this roo behavior.
If it were me though- and I don't know a lot about your set up other than it is super beautiful and charming and I want to live there**deep sigh**
I'd probably toss him out and leave the ladies and mama in the safe space.
Chicks follow their mommie.
I never let young chicks free range. Too many cats and big birds here.