I am so sorry I have not replied sooner, there is litte I can say to help about your employer who really is taking horrendous advantage of you, especially if he has recently been through this. Not someone I think I would like. I just hope you can resolve the issues there or find a better job with a more considerate employer when the time seems right.
Your Dad will be going through a lot just now, not just physically from the cancer but also mentally. I was totally unprepared for the mental anguish Mick had built up over a period of time and had bottled up inside. Mainly because he was afraid of upsetting me or Karen by sharing all of it with either or both of us. He was always quite open about things so I thought he had always told me everything. He did find talking with the pastoral care Lady at the hospice a big help. In fact that is what enabled him to eventually talk with me about all his worries and concerns so we could figure out how they could be addressed.
It was shortly after that we had our big long chat with the Palliative care consultant (as mentioned in my thread about the elephants). Prior to all of this he was also really weary and tired, any emotional distress is tiring but when compounded by the physical strees of cancer it can be overwhelming.
Maybe your GP will suggest things that might help mentally as well as medically.
My very best wishes to you and your family