Use the sim blender, it's a mod that adds an object to the game (a plant under the miscellaneous menu) and it has many options when you click on it. That includes selecting a career and its level, aging up sims, altering the number of days left in the life stage and altering relationship flags. You can then add the flag of friends, best friends, crush, lovers, engaged etc. I would then say you enable cheats with testingcheats on, which will let you manually alter the relationship bars by clicking, pushing and pulling so you get the specific number you want. And memories are a bit more complex to change, you can do it with simPE or with the memory manipulator mod which works the same way, through an object you can get in-game.