Fair disclaimer, I last played the game at the end of 2022. The responses below are based off my memory and might not be 100% accurate. I still hope it's, and is of some help.
Check your questlog for side quests and requirements.
Colin? Did you mean Calvin? If so, and if you did meet Aoife for coffee after talking with Calvin, then the only other requirement that comes to mind might be to go watch movie with Gina and Jo. Then simply head to college the next day, talk to Miss Short and Aofie should show up at college when you exit.
You can't. After dropping off the flyers and peeping on Christy, you reach end of content. Unless by "package", you meant the flyers. If I remember right, you need to go to the work office, open up the "offers" menu and select the box with flyers in it, in order to deliver it.
It's his only simplest choice if he wants to experience that content. The alternative is to play the older RPGM version without the new content that was shared here by
another player.
As for a mod, there is a reason RPGM mods are rare. The engine is pretty complex in that regard as you will require separate plugins to be installed beforehand to manage switches, events and what not, unlike Renpy which is pretty straightforward, as in "dump xyz.rpy file in the game folder directory".
