Russ,
Sorry that you are struggling with ambivalence, over the death of Someone who treated you badly.
Can we explore the implications of it being suicide?
Clearly there was something overly perfectionist and critical in his management of self as well as of others. Something he couldn't find a way to satisfy.
You are here, like the rest of us, to heal, and to find new and constructive ways forward. Something that he could neither see nor it seems, ask others for help with finding.
Non of his faults,flaws or deficits are your responsibility.
There can be all sorts of reasons for going to a funeral. The funeral serves as a sort of act of closure. The person is gone and the ceremony shows that to everyone.
Some may be there to pay respects,
Some to catch up with other people
Some to dodge off work for half a day
Some people may even be there to see that the bastard goes in the hole and stays there.