One of the big problems of a 3 month gap is that you tend to forget what's going on. I completely forgot that the Evil Queen was turned into a snake.
A plot line I'm not really a fan of is Hook killing David's father. That carries coincidence to a major extreme.
It's like there's only a handful of people in the Enchanted Forest. The odds of Hook being on land and coming along at that one time is beyond miraculous.
But rolling with it, the idea of Hook telling anyone is absurd. Sometimes secrets should be kept.
The Charmings though shouldn't react too crazy. Hook was a villain before he met Emma. They know he murdered people. They know he was a terrible human being. Wouldn't it be extremely hypocritical for them to accept Hook now, but then revoke that acceptance because one of the people he murdered was connected to them? If they can accept that he killed an anonymous boy's father, why is it different? Personally, I get why they could feel that way, though morally, there is no difference. A victim is a victim no matter who that victim is.
Regina murdered a LOT of innocent people too and they are ok with that.
My initial thought was, "What a heartwarming story." David was acting all irrational, hellbent on finding out the truth about his late father's fate. He was a jerk to Hook. And once David uncovered King George's apparent involvement, it was Hook who stopped him from exacting revenge and killing the former monarch. Yes, what a noble man Killian has become, or so we were led to think. Why did the writers have to ruin Hook's otherwise reformed character by making him commit a horrible act in his past life? 
If it was Regina or Rumple who was responsible, perhaps it would have less of an impact on the Charming clan. But Hook is family ... or is about to be. 
or should I say, Captain Nemo gave Hook some sage advice: tell the truth to the Charmings or keep it a secret, but learn to forgive himself. In any case, he should seek forgiveness. Emma found out anyway as Hook considered burning the dream catcher and erasing his bad memories in the process. Realizing that Hook couldn't bring himself to tell the Charmings the truth, Emma returned the engagement ring. Hook planned to leave Storybrooke but had a change of heart after Snow told him about the Evil Queen. "Love can [save] even the darkest souls." Just as the former pirate was saying goodbye to Captain Nemo, Gideon showed up and submerged the Nautilus, banishing it from the town's harbor.
