1. Feckful. I had to double check and learn it is, in fact, a word. I loathe the overused "feckless" so I am happy to see "feckful" is a thing. From now on, "less feckful" will be my replacement for "feckless" (though I have no plans to use either if I can help it).
2. Staunch versus stanch. Per Garner, "stanch" is preferable as the verb (to stop the flow, eg of blood); "staunch" as the adjective (a staunch and stalwart friend).
3. Scaramuccian, which, I guess, defines itself.