The floating window style for Rich Media Annotations (RMAs) is defined in the ISO 32000 EL3 PDF specification, but Adobe have decided that if you specify a 1920x1080 pixel window size then that's what you get, irrespective of whether it fits on screen or not. That violates section 9.6.1 of the ISO standard, but it's been that way ever since RMAs first appeared. Can't see engineering changing their minds now.
The position of the floating window can take one of 9 values (equivalent to a pair of top-middle-bottom/right-center-left) but while the latest build of InDesign CC can set those, Acrobat XI and earlier versions of InDesign cannot. Acrobat and Adobe Reader X and later will respect the value.
The "Max" choice in InDesign's dropdown menu is meaningless - there is no "scale to fit" option in the ISO standard, you have to give it pixel values of width and height. Internally there are three values for each dimension (Default is 288, Max is 576, and Min is 72) and when you choose "Max" in InDesign, you simply get those three defaults written to the PDF data stream. Acrobat will use the Default value. I suspect the ID engineers wanted "Max" to do something else, but forgot to code it.
As to getting RMAs working on iOS - not going to happen. RMAs rely on Flash Player, and Apple doesn't allow it to be installed.