They're going to stick out quite a bit, more than what you're already running. Also they will need substantial arch work unless you're running 4x4 suspension or 135 tyres stretched on them. I would leave em. I ran 14 x 8 et 15 and they were quite pokey.
Yeah, but the wheels you're looking at are 25mm wider and have 20mm lower ET which will mean they'll stick out around an inch and a half more. Here's mine on Et15 8's (ET 25 7.5 at the front.)
The bumper is just half coded mate. Nothing more than that.
VW do gen ones or you could get a body shop to smooth out the texture.