Don't worry, we DO understand what you're going through. I know what you mean, with DD1 when I was really struggling about the 6/7 month mark, I found people saying "oh she won't be like that forever" didn't help, it just kind of trivialised the personal hell that I was going through. But then, I probably said the very same to you in one of my earlier posts, so it is easily done!
I'm trying ot think of other constructive things I can suggest to help you that made a difference to us....
Dummy? have you tried her with a dummy? It might take a bit of perseverence at this age, but if you keep at it, you might find you can buy a bit of peace while she investigates it if nothing else. We've not had much luck with DD2 and the dummy, although we did manage to persuade her to have 10 minutes on it when she was screaming in the car the other day and she does quite like just looking at it and chewing it.
Snacks? DD2 can be kept amused for a little while if I give her a piece of dried apricot to chew on (the pre-soaked squidgy ones, not the leathery ones)
Standing - does she like to stand? Is she always pushing up on her legs? lean her against the sofa for a bit, if she's happy to do that. Obviously if she is howling then she's not keen on that!
Music - I have danced around the living room to 9-5 by Dolly Parton more times than I like to mention to cheer DD2 (and myself) up. It doesn't ahve to be Dolly, obviously, but it does need to be cheesy and uplifting for maximum relief from the drudgery of babydom.
Naps - you say you have a hard time getting her to nap. Have you tried putting her in the cot, giving her a gentle stroke and then just leaving her? My DD2 goes through what we call the "Superwobble" if she's overtired and you think her head is going to explode, but after a couple of minutes she conks out. It is far quicker and involves a lot less screaming that rocking and singing to her. Some babies need to cry down in order to get themselves off to sleep.
Sorry if you've tried all these before. But you sound like you;re really having a hard time and hope there is something there that might help. Keep posting and ranting anyway, its good to let off steam