A1: I have a 49" Samsung Odyssey G9
A2: PBP, yes, but I wouldn't say it's convenient to switch -- it's multiple menus deep
A3: I'm not sure I understand you here -- you mean you want the same image on both sides of the PBP? Natively, no, that's not supported, it requires different cable inputs for each side. Since I don't see how you could get that behavior with 2 monitors without some external support, you could just use whatever you're using for two monitors and plug it in twice to the single monitor. If that's not the behavior you're looking for, LMK.
A+: AFAICT, there's no software control support for it.
Oh! Yeah, that'll work perfectly fine. I actually run like that on a rare occasion -- there's some older games that, for whatever reason, really don't support and/or care for 32:9, so I pull an extra HDMI cable out, hook it up, turn on PBP, and Bam! two 16:9 screens.