Ya, The first thing you have got to do is to calm down and stabilise yourself. It is a very good idea to give yourself a break for a few days(say a week) from the regular studies and do something that will cool you down , like reading a nice novel like "Les Miserables" of Victor Hugo, or listening to some cool calm sort of music. If taking a break is not possible i.e. if you still have some exams to give then study and prepare in an easy going and courageous way instead of a tense perfectionist way. Don't take too much tension, it will only spoil your efforts. While practising sums, try to take it as a game rather than as work. Whenever you are not able to solve something, don't get discouraged at all. We all find tons of problems which we can't solve at the first attempt.Just try to have an idea which section of which chapter the problem comes from. Read that section again and while reading, understand and enjoy the concepts therein, instead of thinking too much about how soon you need to complete it.  I daresay that if you enjoy and understand the concepts,  it will take much lesser time than when you bind yourself with time limits and continue to burden yourself thinking about those time limits or goals while studying. Better follow the order of topics as given in the book/syllabi. You may also try doing the topics in which you think you are strong. However in case of chemistry, reading vital chapters like atomic structure and chemical bonding will help you. As for books, the ones that you have are enough for now. Better opt for single books (e.g. only Concepts of Physics for the theory part of physics) Taking a lot of books will only dissipate your efforts. If you have any doubt or is not satisfied with a particular book then of course you can refer other books.  Later on, as you feel that you have mastered the topics then you can do problems from a lot of books. Question-banks containing numerous past question-papers are good for practice. What book do you have for XII Maths?

        I am not in a position to tell you whether dropping a year will be beneficial for you or not, because I haven't yet done any such thing .  many students just waste off the dropped year. But if you haven't any other option left, then do make full use of the dropped year. You should also ask the Goiit member magiclko about this, coz I think she has had the experience of dropping a year ( as shown in her profile).

      

         Now, I haven't any right to talk about your personal or family life or its problems. But still I give you some very general advice. Maintain your peace of mind. Try to remain indifferent towards people who inflict any wrong upon you. Don't burden your own mind by thinking how cruel or unjust they are. Don't like them but don't hate them either.  Just remain neutral,  and don't let their actions bother your peace of mind. You also need to change an idea of yours. Remember that the purpose of all your hard workis not to show them what you can do, but to do something beneficial or meaningful in life, to serve your felowmen.  There is no use wasting your in showing others your capabilities, coz your life is worth much more important things than that. Calm and systematic hard work-work will bring much better outcomes than emotional excited ways,  be it in the case of studies or in any other field in life. 

          Life is a huge game of solving problems.  So, never lose hope even if you face tough ones. If you have faith in God, do pray. It will help you a lot.

         If you need further help,  please feel free to ask again.

                                           All the best.