I bolton, zeroing in on the major plotline points as you have aligns nicely with the paradigm I teach (not the only way to approach story structure, but one which will feel comfortable to script reader or development exec). Let me show you:

I think these are the major plot points

Act One

• Young states that he wants to tend the lantern but Old is adamant about it, “I tend the light.” — The Opening
• Young sees the body of a man floating in the logs. A mermaid swims towards him. — The Hook
• Old says it’s bad luck to kill a seabird. The seabird tempts Young. Young kills the seagull. — The Lock

Act Two

• Young asks Old again about tending to the light. Old won’t let him. — Deconstruction Test
• The tender doesn’t come. — Transition
• Young sees a shrivelled corpse of a man with one eye in the lobster pot. — Reconstruction Test
• There’s a bad storm. — All Is Lost

Act Three

• Old fires him. — On the Offensive
• Old and young attack each other. Young walks him like a dog. Old dies. — Final Struggle
• Young falls from the lighthouse and the seagull eats him. — Denouement

For some background on this paradigm, what I call Narrative Throughline, you can click here to see a GITS article I did breaking down the Pixar movie Up.

Thanks, I bolton, I appreciate your tenacity in going through these scripts and hope you’re learning more about the screenwriting craft!