Dealing with death is the worst and I'm so sorry for your loss. I lost my mom when I was 19 and I couldn't cope with it, and even now... 9 years later I experience moments of horror & grief. It's especially difficult for me too to concentrate on taking care of.myself especially with so much that is going on but we have to try. I am not a fan of exercise either and I'm still trying to find a program that I will like and commit to... but we have to try.
For the most part, I can control my food intake and if it's one thing you can do right (for now), stick to it because it may help you into getting accustomed to more healthy habits. What works for me is tracking an entire day's meals in advance so that I don't mess up.... once you've already eaten something... there are no do-overs.
What helps me deal with anything, from grief to just feeling blue is keeping a journal and expressing my feelings in poetry. Take your time with everything because sometimes we push ourselves so close to the limit that we might do more harm than good. Take care of yourself and being overwhelmed doesn't make you a crybaby!

Grief is a hard thing. But take your time cry when you need to cry. I agree with journaling. You will be amazed at how much just writing down what you are feeling will help.

Don't stop trying to exercise and eat right. Just when you screw up make up your mind that it is not going to blow the rest of the day. Or the rest of the diet.

I understand a little about grief. I lost my mom in March of last year and I had lost my dad 13 years prior to that. Still have moments when the sadness overtakes me. And eating has always been my comfort. Now I make myself aware of what is going on and go climb on the elliptical or take a walk instead of eating. I am not perfect at this by any means but each time I chose something else I am winning.

Hang in there. And we are here for you.