1. I think it's just to torture him to death. I suggests just showing him already there when Fingolfin starts blowing his trumpets, show that he has been there a while and is already starved. My understanding is that we will in Ep 12 convey that Morgoth was torturing and interrogating him in a dungeon underground earlier.
2. Disarray and not being sure what to do next -- Morgoth won the last pass. Maglor trying to lead and being somewhat ineffective. Curufin is challenging his leadership in subtle, sneaky ways that Maglor can't just call him out for. But since they withdraw to the other side of the lake when Fingolfin comes, it seems likely that Curufin isn't 100% in charge. Or that when the pinch comes, most Feanorians do not want any confrontation with Fingolfin's folk (most even feel bad about burning the ships) and want to do things Maglor's way. The whole camp should look, overall, like they're out of their league and despite winning the Second Battle, really don't have what it takes to take on Morgoth without aid.
3. I think no direct interaction is best. Just like in the book: Fingolfin's larger host comes into Mithrim, the Feanorians hastily pack up and leave the north shore to get out of their way. There's tension in both camps, enough so the audience wonders if a fight might be about to start.
4. I suggest: Fingolfin reforging Ringil.
Turgon has the most reason to hate them having lost his wife. So he is possibility and probably the best bet. Angrod and Aegnor, might be ones that just want Feanor punished. Galadriel might be against an execution, but she might want Feanor banished before the rest of the Feanorians are accepted back into the fold.
Aredhel and Fingon will be strongly argue for the sons of Feanor. Finrod too might be on the forgiving side, but from a more genuine place than Aredhel/Fingon. Possibly even having a young Orodreth admiring and siding with Finrod over his father.
I think Turgon is the one who hates them the most, followed by Galadriel -- they're the most likely to say "execute them" and maybe it foreshadows Turgon's decision to execute Eol for killing his sister. But, I don't think anyone is entirely in the "let's just forgive and make friends" camp, maybe not even Fingon yet. That is, I think all of them are angry at Feanor, his sons, and his followers in general.
Fingon, Finrod, and Aredhel are the most willing to consider some kind of qualified reconciliation but not very strongly in favor of that, yet. They don't hate the Feanorians for what they did. I think that Fingon comes to his much stronger "Let's reconcile and forgive and forget!" position somewhat more gradually than that, and is prompted by various things over the next 5 years: the Noldor sitting around doing nothing at all while Morgoth rather obviously prepares for war against them, knowing that Maedhros is in torment somewhere, and remembering when they (and the Noldor in general) used to be friends.