Okay, here we go:
Small Italian coastal town - Sci-Fi Player - Beach Cove 2015, City Streets 2015, and Coffee House 2015, along with the element “motorbikes passing” (from Cyberpunk - The Apartment, or in several of Masks of Nyarlathotep 4, the Egypt sets). City Streets provides traffic and birds, Beach Cove provides gulls, waves, wind, and boat horns, Coffee House provides crowd noise and conversation, and the motorbikes are for the scooters that are so ubiquitous when we think about Italy!
Boat Tour - Sci-Fi Player - Two-Headed Snake chapter 6 Belgian Congo. There is a mood called “Steam Boat” and that’s what you want (likely minus the eerie music for now). You can modify that with additional waves, gulls, and whatever else you like from Beach Cove.
For creepiness, I’d recommend keeping Fantasy Player’s Elements - Horror at the ready. You can inch up the creep factor in any set with that, and it has one-shots for horror stings as well. In addition, Sci-Fi Player’s Nyarlathotep set has a number of great horror stings.
Abandoned Island - for the lemon grove, try Fantasy Player’s Strength of Thousands - Spoken on the Song Wind (SSW) - Service to the City 2. It has the mood “carnivorous gardens”, which would work nicely. I’d add the “creaking trees” element from Exotic Palace to amp up the “rotted” factor.
For the cave - Cartoa Outdoors has a nice mood called “cave” which has creepy music and a nice wet cave ambiance. Flooded Cavern would work as well (as Cartoa Outdoors is a Community set and you need the Supersyrin subscription for it). Sub-Terra (in Sci-Fi player) or Mi-Go Underground, are also great options.
Creepy Forest - try Undermountain Forest for that one, minus the elk and bear elements.
For the pit, I’d combine some of the cave sounds with the forest to emphasize the echoing nature of the pit.
For the abandoned hospital, I’d recommend Government Facility (minus any people sounds, of course). You can add some sounds from Alien Laboratory for mood!
Cave-in - There are two good cave-in one-shots. One is in Tomb of Horrors, the other is in Descent into Avernus - Dungeon of the Dead Three I.
Cemetery - for that I’d use the forest sounds, but kick up any sounds of wind, turn up creepy music, and turn down any sounds of wildlife.
Crypt - Mummy Battle has a great crypt!
Rats and flies - there is a Giant Rat Battle set if you need it, but Curse of Strahd’s Village of Barovia has a “swarm of rats” element. And Insectoid Swarm or Hive Attack can give you all the bugs your heart desires.
Ghost Sounds - Wraith Battle has a lot of good sounds for that, as does Nyarlathotep.
Military - Star Island has some good general military radio sounds, if needed. And then Sci-Fi Player has some universal one-shots for “huge explosion” and “shattering explosion”. Insectoid Hive as a “missile impact” one-shot that, while doesn’t have an explosion at the end, does sound like missiles streaking down (from a plane or ship), and you can add the explosions at the end.
Let me know if you need more sounds! I hope this helps! 
