Hi Maximus,
1) Since your contract already mentions a particular date don't alter that or rather I should say you any discrepancy will make your case complex. So just explain the situation to them and the date on which you would like to fly/ reach Germany.
2) Unfortunately, I can't suggeste concretely anything about Banglore because I applied from Mumbai and the people were very nice in explaining and understanding the things. But yes, I do know certain cases where the people were understanding in other parts so you should prepare your case well.
3) If my understanding is correct you may have already notified your employer about your wish to serve notice period, In that case they may change your joining date. Just get some documentary proof and your case will work fine. (Or otherwise you may ask them to compensate the money deducted for not serving your notice period).
4) Regarding Blue Card- Please speak to the concerned officer during interview because I entered Germany when the Blue card was about to be initiated so I entered on a normal aufenthaltstitel and converted it later to Blue Card in Germany. But I think it may be possible to apply from India if you are fulfilling the conditions.
Oh one more thing if you need core info there is a new office that has been opened by the ABH called SCIF (Service Center for International Professional). So based on your location you can contact this office directly and believe me people will listen to you. That's the best part of being in Germany (with documents)..hi hi

). But ya sometimes you need to push your point.
Oh and yes congrats and welcome to germany. Hopefully, You have secured your contract well. Please go through the thread below it may give you some info regarding your contract.
http://www.trust7.com/forum/-/message_boards/message/749669Regards,