1. Msport 330xi isn't lowered, so it will look quite high when you fit 19" wheels.
2. Many people use 235/35 and 265/30 tires in a staggered setup. 235/35 and 275/30 is also fine for AWD car. Either of these sizes will be an ideal fit on 19x8.5 ET35 front, and 19x9.5 ET33 rears. You could also get 10" rears instead of 9.5" for these tires providing the ET (offset) is correct. If the vender can't tell you the size and offset specs of the wheels, then don't buy from them.
3. Normally an 8.5" rim can accept tire width in the range of 225 to 255, but ideally its best to use either 235 or 245 width on an 8.5" wheel. 265 tires are too wide for 8.5" wheels.
4. Its important to choose the right combination front and rear sizes so the diameter will match as closely as possible, otherwise there can be issues with the AWD system on your 330xi. Some people prefer to use identical front and rear sizes for this reason, but correctly sized staggered tires are also fine.
5. If you are asking about TPMS system, your car is a 2006 model, so you don't have any sensors inside the wheels for the pressure monitoring system. Instead there is a pressure monitoring system based on the rolling diameter using the ABS sensors. That system can be reset from iDrive or using the control lever so its ok to change to non-runflat tyres.
Getting run-flat tyres in 19" isn't a good idea because the ride will be very harsh and they will cost heaps. I think you should keep the standard 17" wheels if you want to use runflat tyres.
Personally I'm not a fan of chrome wheels. For your arctic coloured car I think hyper-silver colour would look better.