As per the subject line, do the number of follower figures available represent a hard limit on the amount of followers you can have and secondly when a follower is eliminated do they go back in the "pool" of followers or are they discarded from play?

The number of figures is the hard limit you can summon. When a figure is killed it is returned back to the pool and can be summoned again. Furthermore, you can summon a figure already on the board to effectively move it to another location (might want to do this when a region is ruined for example).

Thank you for the clarification