Are you by any chance using a save file from a way older version of the game? RPGMaker tends to have problems loading certain scripts once you've already passed the triggering point in the game in the save file, that'd be my first guess if Nick's home doesn't show up for you on the map. That's why each update comes with prepackaged save files, so people don't lose all their progress any time this might happen. As for point 2, that's not a quest, in 0.59 Spedu changed the purple tiger's home, so that merely trying to go up the stairs would trigger the text box asking if you wanna get up there with someone. You can try to re-download the game and use preset save file 02 on version 0.63, which puts you on Pine Island with your party level 22. However, Nick's home has already been unlocked there and his items been picked up, so you won't get the introduction cutscene and additional interactions, I'm afraid. If you're playing public version 0.18, you can try save file 02 on there, which puts you at the end of the Beach Cave, just before you enter the pirate ship for the first time. Yeah, you'll be losing a lot of progress, but at least you won't have to start from the beginning. (If you're using Joiplay, I'm afraid I can't help you.)