Kosher salt is fine and actually preferred.
You can add herbs and stuff to the brine but they may not uptake as much. I would stick to just adding all of your other seasonings and herbs after you pull the bird from the brine. No guessing at how much is needed with water + bird when you are simply seasoning the bird directly :)
You absolutely must refrigerate while brining. You will have to clear your regular fridge to store this while brining lol. If you can put in some kind of ice chest and cover with ice and keep it on ice during the brining period then you would be ok. Or if your ambient temps are the same as fridge temps and you don't have pesky wildlife to mess with it then you can put outside. I can't do this in TX, way to warm here.
If you cannot make the room in your fridge and have no cooler/ice/outdoor temp optins, then I would simply switch gears to an
injectable marinade and not brine at all.
I can't tell you how much or how little injectable to use, you just have to guess hahaha.
As for cure#1, that turns your turkey into the kind of turkey meat you get when you buy a smoked turkey drum at the state fair or at a place like Disneyland.
It's the only way I do my turkey's these days, I love that flavor!!!
Once you get your fridge situation sorted out you will know if you can brine or not lol.