Those scene are all covered in the walkthrough. As for the House Party event, open your save, scroll all the way down to the bottom, find the 2 lines that says: <ChrisParyLevel> and <JessPartyLevel>, edit the value in those 2 lines to 1, save, reload, and start house party event. It should work properly now.
The problem you encounter occur when either one of those line exceed the maximum value allowed for the game to work properly (which is 4). So if either Chris or Jess party lv is above 1 when you start the event, and you increase their mood any further, they will go over 4. All these and more are explained in detail in my cheat sheet (which is linked to in the OP), btw.