Some more comparison screenshots showing why 'widescreen' does not cut it:
http://files.dotbas.net/img/fov-1610-default.jpg (non-widescreen, non-fixed)
http://files.dotbas.net/img/fov-1610-rs.jpg (widescreen, note the lack of vertical information -- widescreen monitors are meant to have more horizontal information!)
http://files.dotbas.net/img/fov-1610-nt.jpg (widescreen off, custom FOV setting, note that the vertical information remains, and more information is added horizontally. this only offers a negligible gaming advantage and as such is not a 'cheat')
It likely doesn't, but that's mainly as MTA's position change code replaces it with something meant for the 640px wide default 'virtual screen', easy to change by editing MTA's source.
That's likely because these values are pooled with other read-only values to reduce the size of the .rdata PE block. III/VC made every instance of a variable with the same static value have a different memory location, but SA's compiler actually pools them to be similar. To change these effects, the code using them would need to be patched, and not the hardcoded values.