Well, the camera was using film, so that is why it worked. As for Amortentia, you desire the character. (I am guessing on the last one tbh)

I think by haunted they mean its filled with strange noises and there are rumors that people have died there

Yep- and as for the Amortentia, it smells of what attracts the person, so that could also include other people. In HBP, it's implied that Hermione smelled Ron's scent in the potion

Creevey's camera is an old film camera. It doesn't use electronics.

The person you love would likely be the thing you most desire, thus Amortentia might smell like them.

The ghosts at Hogwarts are quite peaceful. Imagine a shack full of Peeves.

Okay.. Now I am imaging a shack full of Peeves. That really wouldn't be fun.

People heard howls coming from the shack That is what scared them. And yes, the ghosts were peaceful. They weren't the type of ghosts we see in horror films. They would just mind their own business and occasionally talk to you.