Horror Fiction Help XV

As Halloween approaches, I'm finishing up a couple novels and hope to have reviews up soon, and I'm also watching 1970s made-for-TV thriller/horror movies on YouTube. Meanwhile, folks are still looking for forgotten horror fiction. Who can help?

1. A late 90's paperback cover, predominantly back but with a large white and red clown leering down at the viewer. I remember the author being obscure to me but he had made it big enough to be in Barnes and Noble. Thought it might be Al Sarrantonio but it's not. If I remember correctly it was either a jester or one of those European whiteface clowns. Anyhow... I bought it and the book sucked and had no scary clowns in it whatsoever. Found! It's:

2. A short story about a botanist who created a plant from an ill or dying boy.  I think the twist of the story was the parents' shocked realization.

3. A Caucasian fellow goes to see an old Indian (Native American) in his tepee to make a deal involving some kind of vengeance demon/spirit--I forget what for--and the Indian was in over his head; the demon came and killed him and took off wreaking havoc in the white guy's life. I think it raped his daughter or threatened her somehow. Anyhow, one of the details that stuck in my memory is that he didn't like his daughter's boyfriend because, for one thing, he was too audacious, i.e. he didn't even try to hide where his fingers were stained from smoking pot. Which he was doing out on a country road alone when the demon got him. Best I remember the cover showed the old Indian conjuring in his tepee and maybe the demon coming up.

4. I was reading a magazine a couple years ago, for the life of me I can not remember which but it had reviews for horror/thrillers, etc.... it described one book's plot, about a snowstorm and a group of people holed up in a roadside truck stop type of thing, and they soon realize there is a sniper outside, and won't let them leave. Found! It's:

5. Any information on a story about an escaped killed called "Mad Maurice."  It was in a kids' horror anthology.  I read it in the 80s but it may have been much older.  There was a bit about branches scratching a window but it really being the killer.  It wasn't really that great, but it is a story I have never forgotten. Found! It's:

6. 1980s Playboy paperback... A rapist gets caught... and nether regions are put in his taped-shut mouth.