I fly these regularly...
Row 4 is an exit row at the wings so they are blocked until day of check-in. The seat pitch in that row is not larger and there is a big bump on floor covering some wires to make that seat undesireable anyway.
These aircrafts take only 15 minutes to refuel and get ready for the next flight. The region route is set up to fly between two cities almost continously. So a flight will not be cancelled because they need the aircraft returned. I was once the only passenger. Imagine that... my private jet with two pilots working for me
They will cancel a flight in this kind of region routes if the delay is too much (ie, by 1 or 2 hours) and it gets to the time of second flight. Then they will combine two flights into one, assuming space permits. Cancellation is done both way, both out and in-bound. Remember, no aircraft out means none coming back either.
I think Air Alliance has the older model of 1900, the C series. The newer ones (D series I think) has larger cabins and allow stand upright inside. The orginal one is really like a flying pipe where you have to bend to get in.