In a simul what happens with timing when only one player is left? When only one player is left in a simul, does he have to move at once or does he have 5 seconds per move?
The idea that there is a 5 second limit on thinking time in a simul is just nonsense. Early in the simul when the ordinary players have plenty of time while the simul giver is going round all the other players the player is expected to have his move ready and play immediately the simul giver arrives at the board.

That said, it is not unheard of for a player to "pass" or request a pass. Usually, in a well organized simul, there will be rules saying whether passes are allowed and if so how many (usually only one or two).

The simul giver is also not required to move immediately, particularly when it comes down to just 2 or 3 players. Believe it or not, he is often thinking about tricky positions in other games while he is making moves in the more routine positions and he is also affected by the cut down in numbers and the reduced thinking times.

Back in 1972 when I faced the late Viktor Korchnoi in a simul he rocked back and thought for a minute or two over one of my moves in the opening. He later accepted a draw which probably tells me a better player than me would have won my position ;-).