There is a tool by @drakos that lists who is voting for a specific witness. I thought there used to be a link from the steemd witness page. I’ll find out if it’s still active and link it here if it is.
Voting do not expire, so yes votes from accounts that are no longer active are still counted. Decaying votes is a topic that is discussed frequently, but many have expressed concerns with doing so.
I do know there are many witness forums around discord, but maybe it would be beneficial to do a AMA on chain or possibly an written interview with some to get specific questions answered.
Did you have specific questions in mind?