Never thought that Vlad can be so unlucky... perhaps he is meant to die on that day? :# Never experienced the unplayed vampires died because of the sun.. yet... But, I would suggest if you could repair the game & see if it is still happening? Normally, I will repair the game whenever I bought a new pack.. just in case..
About the plant, you can plant it anywhere..one of my Sims plant a Plasma tree in a greenhouse... and reading the book will not turn you into vampires.. but it will give you tips on how to deal with the undead... you'll become a vampire only if you asked the vampires to turn you into... but, always lock your doors... because, in my game.. whenever my non-vampires Sims read the book, sometimes, vampires will come & visit them.. by breaking in when they are sleeping... and of course, to drink the plasma...
And this pack comes with new lot traits... and one of the lot traits that I like to use is on the dark ley line... my normal Sims couple gave birth to a twin.. one of them is a vampire! :D