"...is OK to just use CO and 0% SF? Also, no need to use PS 80 if not adding scent, right? And is KOH one of those things you can usually buy locally at a hardware store, like lye?..."
1. Yes, it is. It will be very hard on your hands, so you might want to wear dishwashing gloves if you don't already.
You'll have a harder time diluting a LS paste made with 100% or high % of CO and get a thick consistency, however. It's gonna be more runny just because lauric and myristic soaps don't have much of a "sweet spot" where the consistency will be honey-like. High oleic LS has more of a sweet spot and is easier to dilute to a honey-like consistency. As an alternative to diluting, you can just use the soap paste directly on a scrub pad without any diluting if you like.
I use the Irish Lass/3Bees recipe for pretty much all types of household cleaning, including dishes, and it works well enough for me and doesn't tear my hands up.
I don't know of any detergent, including Dawn, that can handle greasy soaping dishes easily, but Dawn comes the closest. I keep Dawn around for pretty much that one purpose, and use my homemade LS for everything else.
2. Nope, PS 80 isn't needed if you aren't scenting the soap.
3. I don't know of any local source for KOH, unless you happen to live close to a science supply house or chemical distributor. I think pretty much all hobbyists buy KOH through mail order -- Essential Depot, Lye Guy, etc.