Some of your questions are rather vague so it is difficult for advice to be given, and others can be found through a quick forum search. For instance, I’ll direct you to this thread to learn how to include a save system plugin to dashingdon: ChoiceScript Saving Plugin (Update: Sept. 2019) - #116 by CJW
From what I see, some of your issues can be solved if you know the basics of coding. (It’s really simple, don’t worry!) Using the guides Carlos posted here will help you in this regard.
As for deciding how stats affect your story and the characters… that will have to be your own creative decision, and it’s something people can only provide feedback upon if there’s a demo to look at. But ultimately, it is your story - so it’s your decision what stats you deem important or ‘useless’.
With this being your first choicescript game, a tip I’d give is to use CSIDE to do your coding. It’s a really user friendly and intuitive interface, which makes it much easier to master the coding process. Error messages are probably going to be something unavoidable, but if you do encounter one you can’t solve, the forum will be glad to help 