320d (F30) questions from a Noob

As per the subject I'm a bit of a noob when it comes to BMW's so please bear with me.

My current wagon is very luxurious and spacious and even though she's very comfortable, her fuel economy is rather atrocious. Normal city/town driving I'm averaging 11.7L - 13L/100km even while driving like a granny and this is on a 70L tank...so you get the picture.

I'm therefore now looking at a 320d Lux line and even though the cabin and boot space is quite a bit less than my current ride, with the fuel economy figures on the 320d I realise I have to compromise somewhere.

So here are my questions:

1. The concept of driving without a spare wheel is a bit strange for me so how easy is it to fix a puncture with the "repair kit" that comes with the car?

2. What kind of mileage can I expect from those Bridgestone run flats? AFAIK the 17" rims on the front and rear of the Lux Line are identical so surely I should be able to alternate the tyres every 10000km or so try to extend the life of the tyres?

3. Are run-flats better (mileage and road handling wise) compared to normal tyres or are they merely there for the "peace of mind" factor?

4. The tank on the 320d is supposedly 57L so what kind of mileage should I comfortably get on a tank if I drive more on the conservative side? I'm sure there are a couple of 320d owners here who can help with this one.

There might be more questions to come but these are all I can think of...for now.

Thanks