Yes, it is the last stop and yes, at times it can be crowded/standing room only or even skipped if the bus is too full. If that is the case, they will send another bus. Yes, you can walk over to Casitas and use that stop. I actually just booked a trip for December and originally had a quote for the Tower and changed it to Casitas preferred for just that reason. I can walk over to the first bus stop easy enough, have no problems walking but frankly, I just couldn't see the draw for paying the extra money for the Tower. The rooms are almost the same as the ones in the non-Tower buildings. The only advantage I could see was you might actually see a view where in the other buildings you have the outside walkway and you would be a tad closer to the food offerings in the Tower. Just didn't feel like enough for me to pay the extra, especially when I could get a room at AKL for less (with my AP discount).