Jess--
I am so sorry for the horrific abuse you had to endure as a defenseless child, and the emotional abuse and manipulation you still endure from your parents as an adult. No one should have to bear the suffering that you have. I am glad that you made it through this period of your life and have become the loving and generous human being who has made such a positive difference for so many other people. Remember, when you are feeling down and dejected, that you are stronger than you know--the fact that you have made it this far is testament to that.
I think all families are dysfunctional to some degree and in various ways, some more painfully dysfunctional than others. I think it is unrealistic to expect a complete lack of emotional or mental sickness in any given family, and that what one should look for is how much love exists within a family. Sincere love will impel people to behave in honorable and thoughtful ways, even if they are imperfect in some of their choices and actions. It's also valuable to remember that one can freely give love to anyone, for any reason or for no reason at all, and that love is not incumbent upon its being reciprocated. At the same time, one is not a bad person for not loving any given person, especially a person who has rendered harm to another.
On the subject of Jack and the dynamic of the Twist family, I make a distinction between what the film shows us or implies, and what the short story spells out. Short-story Jack is far less idealized than how the film presents him, and is not shown as especially loving or tender to anyone apart from the very deep love we come to learn he bears for Ennis. This might be more consistent with the very explicit abuse we learn, in the story, that Jack endured from his father. The urinating incident may have been the single most egregious event of abuse in Jack's childhood, but it suggests that Jack's youth was possibly brutal (it was certainly probably lonely), and serves as a vivid illustration of the strained relations that always prevailed between father and son.
Another element of this episode is that it, to my mind, introduces a possibly sublimated sexual component to Mr. Twist's treatment of his son. The act of urinating on one's child far transcends what would have even been considered legitimate discipline in the culture of the time, and is strongly redolent of sadism and sexual abuse. Jack also notes here the difference between the appearance of his father's penis and that of his own, and of how he could never "make it right" with him from this point on. It is possible that Mr. Twist saw something of his own nature in Jack, and hated him for it, punishing him with emotional distance and contempt.
I'm not surprised to learn that many here come from abusive backgrounds. We live in a culture of abuse, inheritors of a tradition that has seen children as chattel to be used and abused as their elders choose, and are only now beginning to emerge from this darkness into a more enlightened and progressive view where much of what was once deemed discipline is now being rightly viewed as the abuse it always was.