Re: American punctuation and emphasis
You'll find few style guides for American English advocate the use of single quotes in any case. They are pretty much restricted to quotes-within-quotes.
Put them inside and if writing for an American audience, use double quotes anyway. Or italics, if it really is a case of emphasis. I wouldn't put Sparky in quotes (single or double) though I would use it for "middly" (and hope that you'll explain what that means in the next sentence).
I'm not a teacher, but I write for a living. Please don't ask me about 2nd conditionals, but I'm a safe bet for what reads well in (American) English.