I'm sorry to hear about your dad

Don't feel like you have to apologize for venting, though! Everyone does that here at least once in a while.
I agree with Rosario about talking to your brother - or any family members for that matter, since they understand the best what you are experiencing. A lot of times, friends become caught up in their own lives/drama and forget that other people's problems exist, but I'm sure some of them will come around if you really need to talk to them.
It's okay to be emotional, but I would just remember that no matter what, your dad wants you to be happy and live life to the fullest - so don't throw away all the hard work you have put in so far! When you feel like going off-plan, take a breath and think about what you are really trying to accomplish. Are 700 extra calories what you need? Or do you actually need to talk to someone about how you are feeling?