1. Do we include the Battle of the Lammoth (but without Argon)?
The idea that Fingolfin's Host marches down the coast to Lammoth might be something we could incorporate into the story. I'm not sure we'd want to send them that way, but it's not like they know where to go now that they're in Middle Earth, either. They want to find Morgoth (to kill him) and Fëanor (to make him pay), but they don't know where anyone is, nor do they have a map to follow.
So...what do they do? Send out some scouts to explore, while moving the Host south into more hospitable lands?
Certainly, they could encounter orcs, but this is the time of 'look, new moonlight!', so no doubt the orcs would be a bit timid. The moon still sets, of course, so it's only out for some of the time, but I can definitely see that being an issue for a standing army of orcs in the field. Not as big of an issue as sunlight, but still, it's *brand new*.
I am fine with including a skirmish of some sort with orcs, but that likely means that Morgoth then knows they are there. Maybe we just have them march off the Ice and start exploring Beleriand in the end of Episode 12, and then show some sort of skirmish/encounter in Episode 13 that leads them to march to Thangorodrim?