AI difficulty can't change, but most of the 'difficulty' comes from player modifiers; just change your own difficulty. This allows for the setting of multiple player difficulties (so a stronger player can have a harder difficulty).
Ping should be back in 3.13 I believe.
MP eliminates some popups, like wonder videos, because they interfere with MP timing (if you have to click through a wonder video, you could be in the process of being killed...) Others are modified by the "minimize popups" option, which causes tech notices and build notices to go to the end of the turn.
The AI is aware of victory types, not sure how well it adjusts but certainly conquest it's well aware of
You can remove the "time" victory option, I believe. Haven't played around with that much. You can always play longer games (marathon, epic)... MP usually ends well before that anyhow.