Forgive me for whatever I said or did
There is not too much sense in this sentence. It is full of empty words that carry no real meaning or emotion. By saying it you let the person think that you are not responsible for anything and that there is not much you can or want to do to change the situation for the better.
I feel guilty for what I did, and you should feel guilty for what you did
This apology involves the other person without his wish. Express what you think and stop imagining what the other person might feel. If he wants to say something he will do it without your help.