1. A vet gets involved with a black magic group including a man tattooed with the tree of life. UK paperback cover pictured the tattoo.
2. A man imports a hyena for his sick son which escapes and causes havoc in the city....I thought this was Graham Masterton but it does not fit any of his titles. Found!
4. 1970s novel (sci-fi/horror) has to do with some space arachnid. Cover shows a window washer (high up on a skyscraper) coming face to face with some sort of alien spider humanoid thing (presumably from outer space). I'm guessing it's from the late 60s or early 70s, because of when I read it and the sexual content (I got it out of our local library when I was a kid). Found!
5. It was 'satanic horror' but pretty mild. As best I can recall the main protagonist was a man who fell in love with a young woman with a mysterious past. There some lingering threat... something to do with her father and the place she'd grown up. The only solid memory I have is that there is a trunk that holds some key to the mysteries of the past. It isn't until the end of the book that the protagonist manages to open it and know the contents. They reveal that the father and daughter had had an incestuous relationship and that they'd worshiped Satan/devils/demons. At the end of the book the girl has gone missing, as completion of some pact the father had made (I think). Found!
6. I never read the stories but heard them from a kid in my class at school way back around 1979, so don't know if they are from magazines, pulp comics or just urban legends/folklore.