I think a vault setting would be too limiting for a novel. A vault you wind up exiting (by yourself or with other vault dwellers) would be pretty similar story-line wise to the games.
I think a good novel would follow a character from PreWar, into a vault, and then out of the vault, into the post fallout world.
Regarding the sub points: A novel is generally considered to be anything from 50,000-175,000 words.
I think Wolfman’s Weston is a considered a novella.
Old Andy, Lorca, and Goris the Scholar have written and posted full-length novels on this site. (Where are you Goris?)
I have also posted a novel on here as my sig line (and Skirt and WolfMan’s kind words) imply. (Child of Atom series is 110,000 words)
Sadly, Zenimx/Interplay/Bethesda will NOT grant you publishing rights…even if you gave them your soul. So its purely a labor of love : :fallout: