The host can fire a companion and the person who joined re-hire them. That should hopefully be fixed in the update planned for this week.
Most of these are known issues, other than the water that didn't electrify (just random chance of triggering, or maybe because it is running water rather than standing?) and your fog of war...
Had you cleared the town area in a previous save? maybe something got carried over from a single player game? (there is a bug where that can happen with quest status in some cases).
