It sounds like you are doing honest grieving for your dad. (((hugs))) It's ok. Try and tell yourself that this won't last a long time, and allow yourself to cry and grieve without thinking that the sadness won't go away, or will plunge you into a long term depression. Thinking that it is temporary will help that NOT happen. The sadness of grieving will then come and go for a time... if you remember this, you might not become afraid of it.

I understand about not being able to be there for your mom. That happens sometimes. She is an adult and needs to have other adults be there for her, or to rely upon the professional team to help her. She needs to follow their advice. You can send a card, telling her you wish you could spend more time but that right now you can't, or such?