Sounds like you have given this plenty of thought, and already proposed burial options that may satisfy both of you.
I did mean that the funeral with relatives would still go ahead, but you would only attend something personal, as an extra to the traditional funeral.
You could also opt to go to the big funeral as final gesture to him.
However, suffering people who are ‘family’, but have sent you nothing but negativity, is not something you are obligated to do.
Other commenters can say you must do this or that for social convention, but only you will understand the amount of actual love and care felt from these relatives.
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Regarding the prebought plot, where you are buried is entirely your wishes and choice. The time is now to make it understood (clearly detailed in your will is best) where you want to be buried, if that is another important choice for you.