Biteypup sounds very similar to your pup @ClownsandCowboys She was a mental lunging biting fuckwit and quite frankly I didn't like her one little bit
The first 1 to 1 trainer we asked to help us recommended lots of mental stimulation and activities, etc. It just made her worse as she was so overstimulated the whole time. Luckily that trainer let us down for the next appointment and was flaky about rescheduling, so I sacked her. Best thing I ever did!
I asked the trainer who runs our normal obedience classes if she would consider seeing us for a 1 to 1 and thank dog she agreed! She said we were doing way to much stimulation and not enough sleep and I was trying to keep her busy the whole time. She recommended the scheduled sleep pattern - 1 and half to 2 hours out of the crate and 1 and half to 2 hours in the crate for sleep. It was a bit of a logistical nightmare to start with, but what a difference immediately! She was much more controlled in her moods and in the end when she was tired she would get her kong and give to me to signal that she was tired and wanted to be crated for a nap. Bit of a nuisance that she doesn't self regulate her sleep, but much more managable as a result, so I'm not complaining 
We did use the crate for a short time out if she got OTT with biting, but literally just a minute or so, just enough for her to calm down and not be getting any reaction whatsoever. That was what she craved when she was biting. If we pretended to 'be a tree' as the first (crap) trainer recommended, she would just keep lunging and biting until she really hurt you and you couldn't help but yelp in pain
Stair gates are another option, but we found the crate time out more useful, as on the way to get out the stair gate she would still be trying to attack you 
Lordy I do not miss that stage!!