Currently, the plan is to have Bëor introduced, then have Haleth introduced, and after that introduce Amlach.
So, a more likely progression at this point is:
- Bëor meets Finrod
- Haleth at the Stockade
- Death of Bëor
- Council
I agree with you that the death of Bëor can easily lead into the Council meeting - but we want Haleth to be an early story. We're not going to wait until Episode 5 to introduce her; she will be dead (well, out of the story, anyway) by Episode 7, most likely. It is very much possible to have Haleth born in Beleriand and have the stockade battle happen before Bëor's death.
I think we can tweak Morgoth's strategy to be whatever we need it to be. But again, keep in mind the tension in Angband's leadership structure. Orc armies are sent out by Gothmog, and are thus not necessarily connected in any way to Sauron's spying and deceits.