RE: How long since a witness' last post, last vote, and how many votes do they have?
This ranking list provides a different perspective about witnesses, but it might be misleading. The witnesses are ranked by the total VESTS of their voters/proxies, not the number of votes they received. For example gtg is #7 in terms of votes received, but he's #1 on the witness ranking because he has the most VESTS received (https://steemd.com/witnesses). Also, this list includes inactive/disabled witnesses, like nextgencrypto and pumpkin. Speaking of @pumpkin, he is very low on that list, but he holds a massive value in VESTS because of proxied voters, mainly coming from @freedom. It's a complicated thing to follow and get clear picture of what's what.
And finally, I checked this yesterday, I'm getting rewarded 0.946 SP per block. The top 20 get 1/5 of that, so that's 0.189 SP/block.
FWIW, I see this as a first pass to see where the votes were landing, whether manually or by proxy. Agreed, it gets rather complex when accounting for the VESTS.
Also, as you've pointed out, it is rather interesting/disturbing that a large number of votes are with inactive/disabled witnesses. Someone ought to submit that as an issue in GitHub or go so far as to create a Pull Request. Any takers??