Your marks are very less in the class 12 and you need to do a hard work for the AIIMS. Noe as per the my opinion do not go for the class 12 again and it would be better that you go for the AIIMS coaching only and if you do well in the AIIMS coaching then you will be able to crack the exam. Doing again the class 12 will take one extra year and it is better to invest that extra time in the AIIMS coaching. It will help you a lot and also you need to do some extra work for the AIIMS.