First of all, I’m sorry you are going through such a difficult time. We can help with connection after he passes, you will be able to have one, it just takes time and determination. When we are experiencing acute grief, it can be harder, but the time will come when you’re ready. You have kind of a unique opportunity to go and say everything you want to say to him, even though he is unconscious, his soul is still with him, it may be coming in and out of his body but regardless he will be able to hear/feel the essence of what you express. This will be more important for your healing and your transition through this process. Tell him your regrets and why you feel guilty, then release those emotions as much as possible.
As far as bad places and hungry ghosts go, please do not fear that for him. He has loving guides, healthy seated ancestors and more helping him transition. Encourage dad to go with them and that everyone he loves on earth will be ok, he doesn’t need to stay to make sure of that, but he’s welcome to come and connect with you all after he’s done his life review and rested/received loving energy to heal from this life. I personally don’t believe, and have never heard from a spirit, that there is any bad place. What does happen is a review of the persons life with their guides, and a panel of ascended masters were they watch their life in review, and if they hurt anyone they then feel how the other person felt, so they can understand. If they had a particularly rough life or were an extremely negative person, they are separated from the rest of their soul group for a time after returning to the spirit world and are basically showered and cocooned with extra love and energy, the negative stagnant stuff gets scooped off and replaced with source/love energy. I firmly believe every soul has a choice in reincarnation, and what they are in their next life and that they agree to it before hand. I don’t believe anyone is forced into reincarnating into anything they don’t want to be.
This is all from things I’ve read, and my own experiences speaking with the spirits of deceased humans, my guides, etc. Some great books to check out on what happens in between lives are Dr. Michael newtons “journey of souls” and Dr. Brian Weiss’ “many lives many masters”
Sending you lots of love OP.