You should def watch the 1992 movie version of Dracula - it is VERY good! (Also VERY horny but like, Stoker didn't realize how horny his book was while he wrote it so like, tracks.) Also I loved listening to Dracula on audio, so if you're ever planning to reread it, I'd definitely recommend it on audio.
Those first couple of Discworld books aren’t that good. There are several series within the whole of the Discworld series, and you can freely jump around between the different series as long as you mostly read those books in order. For you, I would recommend you jump straight to the witches, starting with Equal Rites or Wyrd Sisters. Since you enjoy Japanese culture, you also might like Interesting Times. My first Pratchett book was Thief of Time and that one remains a favorite. You by no means need to read the second book at all to understand the series.
I think I knew that we didn't have to start at the "beginning," but it's also hard to know where else to start! My husband got a few more Discworld books for Christmas, but I think for now, those are going to be things he reads on his own. I think I prefer being read middle grade the most, so we are going to do that for awhile :) but I appreciate your suggestions!