So if you are doing multiple spawn points but want them all to contribute to an overall number of spawned enemies, I would have the array of spawned enemies and all subsequent logic stored somewhere else rather than the spawner itself, probably the game mode or game state, then do all the checking there. Just let the spawn points handle the actual spawning logic.
In terms of the overlapping actors/box collision, it might be to do with the collision profiles? It is hard to diagnose without seeing it.