Nice haul. First, disassemble the shutter arm and clean the spring and gear teeth with isopropyl. Old rubber is probably cracked—swap it for a new 2‑mm silicone strip. Then re‑tension the spring by carefully winding it a few turns; if it still won’t budge, check the counterweight—it might be off. After that, put a fresh batch of fresh film in the tray, crank the lever a couple of times and listen. If it still sounds like a dead weight, you might have a gear stuck in the drive—clean that with a cotton swab and a touch of mineral oil. Done.