Horror Fiction Help XXVII

I'm calling upon you again, dear readers, for assistance in identifying some forgotten horror tomes of yesteryear. Several are apparently from horror comix/magazines of the 1960s/70s, which are not really my area of expertise. Thanks in advance, everyone!

1. I read this story in the late 70s - early 80s, I think its from one of the DC horror anthologies as I definitely read I, Vampire in them at the time. It feels EC but I don't think I had access to any EC reprints.  Ive had no luck finding it since.  Here's what I remember.  A rich businessman decided to fake his death and live isolated from the world.  He has built an entire computerised home under his tomb where he plans to live with the help of his assistant who he contacts via his computer.   The assistant double crosses him and the air starts running out.  He flees to his escape tunnel but finds it filled in with dirt.

2.  All read in my teenage years, (1960's). All from paperbacks or comics from the time. If I had the authors names I would probably have had more success, but unfortunately, no. The first was entitled "Talent" about a precocious young boy who possessed the gift of being able to make things happen or change just by thinking about it. The spell lasted as long as he kept thinking or concentrating on whatever it was, then, when distracted or bored, it would revert back to whatever it was. During a visit from his parents friends/relatives, he demonstrates this power to a little girl who comes with them out in the farmyard by turning a pig scratching itself against a post in it's pigsty into a life size porcelain piggy bank just by thinking it. The girl asks if it will stay like it and he explains that if he stops thinking about it, it will regain it's original form, but when he tried it with a piglet sometime before, he smashed it with a hammer. Then, later, when he'd forgotten about it, the piglet retuned to normal but was " all broke up and bloody...". The nasty little shite gets his comeuppance at the end of the story in a pretty similar fashion. Found! It's "Talent" by Theodore Sturgeon; widely anthologized but first appeared in "Beyond Fantasy Fiction" in 1953.

3. It concerns a university student desperate to pass his graduation in maths, trigonometry and geometry. Being lazy, he decides to try an alternative route of passing his grades with black magic and proceeds to bone up on how to elicit the help of a demon held under his control whilst within a pentangle drawn on his study floor. After careful preparation, he goes through the ritual and succeeds in summoning a demon within the chalked area before him. After the initial shock he tells the demon he will keep him there forever if he doesn't help him pass his grades.  " You see...." he says to the demon,  "...I'm absolutely hopeless at geometry...."  Before he can continue, the demon, looking down at the floor replies "....you're telling me..." and steps over the useless pentagon he had drawn. Found! It's "Naturally" by Fredric Brown, which has been anthologized many times, and can be found in his 1958 collection Honeymoon in Hell.

4. The plot of the horror story involved a man who survived an awful killing? lived in a mental home. He drew pictures with white shoe polish and charcoal. There were teenagers and one of them had an older sister who was taking care of the crazy old man while she was having an affair with the local policeman. Two of the teenagers were caving and found luna moths, which had something to do with the plot. There was a woman named Birka who had become one of the creatures that killed the crazy man's family--she might have been his mother but she was with the creature. They were using strangler vine to stop the creatures and if anyone got one of the killer's thorns embedded in their skin they'd turn cold and deadish like the creature. It seems like it ended with one of the teenagers getting a thorn in his foot. Found! It's Fiends (1990) by John Farris.

5. I saw it in 1984, so it was likely published in that year or 1983. The cover showed a body on an operating table, covered with a sheet, and with those big electrode things overhead (like from the Frankenstein movie).  I only remember the blurb on the back cover. It went something like this: "_________ asylum. They warned him not to go there. But his son has disappeared, so he must dare. Now, from a window in a cell in the asylum, he watches as a group of lunatics lower a child-size coffin into the ground. The coffin moves. The boy is still alive. But no one can hear his screams over the howls of the patients, no one except the woman who is waiting in the asylum, and the doctor who is preparing the final experiment." Found! It's The Bad Room (1983) by Christopher Cook Gilmore.