i'm not sure that skype do upgrade by itself?! try to diseable "automatic upgrade" option in goole play. i'm use to use skype on different devices and never got situation that upgrade is done by automatism.
resolution in skype is not possible to set by number, only with last item in settings "video quality" -> high - low. but i'm always use it on high, so i can't tell is there any big difference.
few months ago, and few pages on this topic back i posted question about camreras, and seems that little number of users use skype with box so i didn't get my answer - same as yours. and in the and, instead HQ logitech 270 i bought logitech 210 camera. just because of slow video and because everything was wery slow and laggy because high res camera.
and you english is very good! ;-)