@Rhiannon58 I guess I can answer a few of those.
If you turn off supernatural beings in the "Options", newly generated sims won't be of that supernatural kind. This setting does not affect your own sims. The zombies you see are just temporary. You can turn them off by eliminating the full moon phase (if vanilla). Master Controller gives you much more control in this regard. You can set percentage limits for every supernatural type separately. If I remember correctly, zombies were handled via Retuner.
I think it's technically possible your sims can become zombies, but I have never seen it, which means it's probably rare. I'd advise to place at least the elixir consignment store somewhere in your town. Cure elexirs (the standard ones are sufficient and very cheap) are on sale occasionally. Or just make your own. Level 2 alchemy is enough for them, Red Valerian and Mandrake Root are needed (pretty much always on sale in the store, in case you don't have them in the garden). The elixir also comes in handy if you get toadified, unless you have someone capable of casting a sunlight charm.
You can evict families and put them somewhere else, yes. If you don't place them anywhere, the game will delete them. Story Progression will keep them as homeless sims, if I remember correctly. Getting them into the game again in that case is difficult, which means you should have a place for them ready, if you want to keep them.
Yes, there are premade houses available already in the base game, and more with some EP's.
University visits freeze time (this includes aging). You will return at exactly the same moment you left. You can send several sims together, but all of them have to be from the same household (your active one), and they have access to the full household funds. Keep in mind that university, unlike in real life, is a cash cow that keeps on giving, if you want. With two students, you can return with more than 100,000 simoleons more than when you came, if your sims study and you follow the "apply for additional funds" schedule.
Non-active sims will sometimes get random degrees assigned, yes. There is a specific subject at university for career criminals available though (the business degree will give you the benefits).
Yes, a university degree lets your sim start at a higher career level from the get go (level 4 with an A, level 3 with a B, etc.) and also means a lot more money from the career (also depending on the grade; x2.5 with an A). Of course, you can also choose an additional trait at graduation.
