I've been trying to make sense of the confirmation process, and am not really an expert, but as I understand it for more distant than a 3rd cousin you need to triangulate, which means you need another match on the same segment within the right range of relations.
To answer your question "Is it even feasible to even confirm that far back?": Yes. I'm kind of hoping to do a triangulation with a couple of my 4th cousins, myself - our common ancestors were born around 1800. No biggie.
I don't really know what the rule is on your last quandry, but I would think that there should be no reason why you can't easily confirm you common ancestor, without confirming the spouse at the same time. In fact, I'd say it's preferable, in a way. Usually you don't know which parent the DNA segment came from, but in this case you do! I think you don't normally mark the common ancestors in triangulation for that reason, but in your case you ought to be able to.
But with 191cM, you don't need to triangulate anyway. If I remember correctly you get to mark the common ancestors, when the matches are close enough relations. If the rules aren't what they should be, I'd recommend using common sense and just marking the one common ancestor even if the rules don't say to.
Speaking of the rules, I guess they're in flux anyway, so I think I'll wait and see what they come up with, myself.