the hairline crack stuff does sound like a load of shit.
do you actually want a new car, or are you just frustrated with the expense?
$300 a tire? That's a bit rich if you aren't running 18s or 19s. Discount Tire Direct has Bridgestone Potenza RE960 AS runflats for $141 each for 16s and $187 for 17s. Hairine cracks? If they aren't leaking air don't worry about them. And a $700 oil leak? WTF? Sounds like you need to find an indie BMW mechanic pronto. If you think you are going to get rid of it you should throw some used non-runflat tires on it for 40 bucks a wheel