I am so sorry for your loss. And for your whole family.
And everything is so hard when the relationship was challenging, it seems much more complicated. Especially when there were also good times. I am sorry you are in such pain.
When you have an early loss, such as the way too early loss of your father, the grief from new loss can trigger an even deeper and more pervasive sense of loss when a new loss happens. I know my friend went to therapy for the first time after a similar sequence of events.
The format of the memorial sounds lovely.
Figure out if everything that seems urgent really is. And take good care of yourself.