I'm sorry for what you're going through. It would be difficult to deal with all the funeral plans and the event itself, along with people's expectations for how you 'should' be feeling/grieving, etc, considering the history/experiences you have had with this man. He sounds like an a$ $ to me!
It's understandable you would experience some guilt, but I don't think you are so much obligated to feel grief really, or to feel guilty because you don't genuinely grieve his passing ..... it's OK to feel relieved he's gone, or to feel like it's a chore or a burden to deal with all the funeral stuff. It's how you feel, it's OK. But you don't need the burden of guilt on top of it .....
I'm glad you're doing things to take care of/prepare yourself for it, seeing about meds ....
You will survive!