Stocking up makes no sense in Factorio, it’s more about a steady flow of resources, keeping up with the demand. The stock will mean nothing if you can’t keep it up. You should keep a small buffer to compensate for fluctuations, but anything above that is actually just a frozen asset, that could be used more effectively elsewhere. I don’t want to be rude, just wanted to point that out. Have a good day fellow Engineer!

Depends on how long you plan on working on that factory. If you want to stock fuel and then start using it until it runs out, then the quantity is up to you, but after that it’s lights out. I’m partial to automating production. That way there’s always fuel going into the reactors, but you won’t be able to brag about the size of your stockpile.

No, just go for it.