Your dp has hurt your child - he left a red mark when pushing you.
You say he says it wasn't rape according to him - well he would say that wouldn't he? He raped you. He's hardly going to admit it.
Why worry about spoiling the relationship you have your in laws? They are as vile as him, trying to scare you in to not reporting what he's done, just so they can keep you (and more to the point your child) close.
You say your MIL used to be sweet but now she has been sneering and you don't know which to believe is really her. Think about it - if sh was genuinly lovely and kind towards you would she have acted as she has done recently? Covering up for her abusive son? Trying to frighten you in to not leaving? No. The real her is only intrested in her son and grandson. She was happy to be nice to you if that kept the grandson close and while you were doing as you were told. As soon as you stand up for yourself she has shown her true colours.
I beg you to leave and seek help. For your sake and especially for your child's sake. This is not a safe and loving home for either of you. These are not people who have your best interests at heart.
I am so sorry that you own family have let you down, but you have admitted you didn't have a great homelife growing up so maybe their idea of what is a good relationship / what you should accept is all wrong.
There are plenty of people on here who agree that you are in an abusive relationship and you need to safely get out and get help. There will be people in realy life who will be happy to support you.
Your husband and inlaws are acting aggressively / ganging up on you now as they know you are being ill-treated and they know they will be in trouble if you report him. They know that will threaten their relationship with your DC, which they want to have control of.
Please don't let your DC be brought up around these people who will turn him in to his dad.