Speaker distance

I think I would prefer the speakers on the long wall. You could separate the speakers by a good amount and still have space on the outside of each speaker (assuming you can center the system on the long wall). I think you could space the speakers about 9' apart and pull them out about 3' from the front wall.  That would be my first attempt, anyway.  Make adjustments from there with the spacing, toe-in, and your listening location. 

A different approach:

https://forum.audiogon.com/discussions/review-sumiko-speaker-set-speaker

There is only one sure way to optimize speaker positioning in a room and it is by ear. Mathematical formulas, ratios and triangulations as well as manufacturer guides are merely starting points and should not be considered as absolute. Also one speaker manufacturer's guide to placement will probably not work for another's. Take your time, experiment and tell your wife you will the final determination on the basis of sound quality, not aesthetics.

If you sit on a high back chair / couch, it will block some rear reflections. Having the speakers toed about a foot wide of the ear helps with this as it uses the back of the chair / couch (instead of rear wall) for reflection. I have wide dispersion speakers for mixed movie/music and have it toed 3 feet wide of center as a balance for multiple seating.

There are mathematical ways for determining acoustical properties (Bostons Symphony Hall was built this way) but you'd probably need to hire a team of architects to design you a new home. So I'd just recommend trial and error. Personally, I own five and a half feet tall Quad Electrostatics and the recommended distance from the rear wall is thirteen feet with side clearance. I've found that nine feet sounds the same to me. However, given that they're not pushing air, I can sit fairly close to them if I want.