1. Can't really tell you about statistics, but you certainly shouldn't base you decision on them. Playing the statistics game is a waste of time. Apply to the college you think will suit you best.
2. No, it's not a reassuring 'myth'. If they're not able to offer you a place at Balliol you will probably be interviewed by another college or colleges. Even after that, you can still be made an offer by your original choice of college. And they won't be prejudice against you because you didn't apply to their college first. If you really deserve a place but they currently do not know where will have spaces avaliable, they can make you offers where your college is not specified until after everyone has received their results.
3. £750-1321 per term is a very respectable rate. Oxford and Cambridge are a lot cheaper than most other UK universities for accommodation, as it is freuqently subsidised by the college. Standard rent elsewhere can be anything from £80-£160 per week, for a contract that includes paying for the room during holidays. I'm not sure exactly, but many colleges allow you to choose what band of rent you want to pay, and you can of course, choose the lowest one. If money does become a serious issue, and would compromise your attendance at the university, the college is often very supportive financially. You may qualify for financial support anyway, but I'm unsure of funding avaliable for EU students.
4. I don't know much about the Abitur but generally, the better the grades the stronger your application.