You are not really over-thinking it that much but you are probably worrying more than you should. We all do. It just comes with hatching, especially the first time.
What I suggest is that you get rid of the Layer pelelts. It has too much clalcium for growing chicks and can cause bone deformation or liver damage. Not that it does with the first bite, but over time it can cause damage. I feed Starter/Grower combination to the entire flock. Starter, Grower, or Flock Raiser will all work, but that combined Starter/Grower is what I have available at my feed store. Then make oyster shell available on the side in a separate container. Your laying hens will eat the oyster shell and the others will pretty much leave it alone. They might eat a bite or two, but not enough to hurt them. If you try putting the layer up high where the chicks can't get it, Mama will pick up pieces and put it down where they can get it. And in just a few days, they will be flying up to get it anyway.
I've seen a hen get chicks safely down from a 10' hay loft. 8" is nothing. Mama may take them back to that nest to sleep at night or she may take them to a corner of the coop. They should have absolutely no trouble going up 8", but if you want, you can put a brick or something they can use as a step. And the first night, you probably need to check on them at bedtime to make sure they all did get in. I've had a broody go to a nest a little over a foot off the floor. Some chicks made it and some chicks needed help the first night. The second night they all made it.
What I suggest you do is put some water and chick feed, whatever you decide to use, on the floor of the coop where the chicks can easily find it. Don't be too surprised if your older chickens decide the stuff you put out for the chicks is a special treat and much preferred over what is in their feeder, even if it is the exact same stuff. It is amazinghow hard chickens will work just to make your life harder when they get the opportunity.
The way I do it, after Mama brings them off the nest, I put her and them in a prepared area where they are locked away from the other chickens for a day or two. It is great if this is in the coop where it is nice and protected from predators and the weather. I keep food and water in there. Then, after they have learned to eat and drink without competition from the older hens, I let them go. I use one of those red chick feeders with somewhere around 20 to 22 opening for the chicks and put that under this thing I built so the adults cannot get to the feed but the chicks can. The chicks can enter from the ends. I just put this out in the run where they can find it.
Good luck!
