Try Manuskript (the developers intentionally misspelled the program.) It is an open-source tool with many of the features of Scrivener. This will give you the opportunity to figure out whether or not a program of this caliber will work for you. If you find yourself needing more, take a hard look at the features available in Scrivener to see if it is worth making the jump.
I say this since it will be an easier pill to swallow to try the free tool and then copy everything over if the paid solution is needed then it would be to pay for the premium software and then find out that the free solution could do everything you need.
For the editing, I would use a premium version of ProWritingAid when developing the first draft and then leverage the power of AutoCrit to help get the first draft looking as good as possible. Take the time to actually look over the suggestions and follow them where it makes sense, while also studying a grammar text. Doing so will help your writing improve, making it easier to find a publisher when the time comes.
Additionally, if you go the self-publishing route I strongly suggest you track down Kindle Create. It is similar to Vellum in the same way that WordPad on Windows is similar to Microsoft Word. You will be able to build a decent ePub file suitable for uploading to Kindle Direct Publishing.
Now - you mentioned concerns about avoiding writing term papers. I hate to break it to you, but a decent chunk of the front work for your story will feel remarkably similar to dealing with a college term paper. You will need to develop an outline, research the environments, settle on the characters you want to use, and ensure that you won't be doing anything to annoy others whose stories intersect with yours. That is going to involve a great deal of legwork.
I wish you the best of luck!