Returning to one's husband after a divorce

My father has recently passed away and he got murdered brutally by a man who hit him on his head with a knife and then slit his throat whilst my dad was still alive. I loved my father very much and it feels to me that somebody has killed me brutally. I am worried that my father may be in pain or discomfort in his grave. I read surah mulk at night but I feel very restless.

Also I have recently been divorced (1 year ago) but my husband gave me verbal divorce and now he says that he can bring me back only if at the cost that I accept his terms and conditions once being that I may not be able to work for a while. I don't want to go back to my husband as I hate him now and I want to consider someone else (my colleague) who gives me the respect I deserve and loves me. What do I need to do in this situation? If I don't go back to my husband, would it be a sin? I feel frustrated that I haven't done enough for my dad and he may be suffering... I can't sleep and I have arthritis and fibromyalgia which aggravated my muscular pain when I am in stress. Sometimes I just think that I should die as all this frustration and worry for my father is killing me and I feel helpless.