Clutter up the run and/or move around existing clutter, and make sure no hiding spots form dead ends that chicks could get trapped in. Having multiple feeders available helps too as food is another resource that can get guarded.
I'm currently integrating my 3rd batch of chicks on a brood-along...
From my experience it goes fairly smoothly, the chicks will stay as a subflock until they get close to point of lay, and then that's usually where you'll see a bit of pecking order jostling as they merge more completely with the adult flock.
It's because everything about them screams I'm delicate, I'm fragile, I'm helpless... but after the first batch you realize that's not quite the truth. Yes they're fragile but they're also tougher than they look, and their natural instincts do a good job of getting them to look for food, water...
I'm a true monster, 2-3 day old chicks go immediately into the outdoor brooder. :p I can't stand the constant peep peep peep, I just want them to grow up!
At 5 weeks old, healthy chicks can handle 45/50. Get them outside during days (a bit of the early evening too would help expose them to...
There's no need for lullabies. Yes you're spoiling them. :) If it's in the 70s at night they 100% should be out already, no heat (or lullabies) needed.
They're used to having a light on all the time. When you turn the light off, are you gradually dimming it or turning it off all at once? If it's latter, that's scary to them.
If you don't have dimmers, another option is to put them in a room next to a bright window and let the sunset decide...