1)They probably limited it to 16 bots because more than that would either crash the game or make it really slow, play with 16 bots and get a view of them fighting in an open arean, and even on a powerful computer like mine it starts to slow down with all the progectiles and gibs flying around.
2)Well the bots are smooth like that, depending on the skill level they are at they will either see you no matter what and kill you, but on lower, from personal experience(ummm ok), they dont see me untill i fire at them then they whip around and make salsa out of me.
3)Honestly it may be just you there are 32 bots to randomly choose from and if your choosing 16 the majority will come out of the first 16 so it will seem like its not going above bot 16, or im just stupid and it a bug in the game.
People are the root of all problems, no people, no problems