Hey, sorry, I was working all day yesterday and didnt get a chance to come online.
Startup repair has seemingly fixed all my issues. The laptop boots in less than 2 mins, and everything's running quick and as it did before. I have no idea what it fixed (I went to bed long before it finished), but it worked!
Thanks for all your help. I learned how to do several things throughout this process that will help in the future, too!