There is a lot of information to process and I think your vet is probably on the right track. If it isn't pain, it is brain. Hopefully you can get to the root of it and help her feel more level. I would guess some sort of regular mood stabilizer will end up doing the trick from what you have said. Maybe prozac isn't the right one. It sounds more like she would need something similar to what they use for people with PTSD. Maybe not anti-depressant but anti-anxiety? Sounds like your vet is fully on board to figure out something.
To the crying if outside and toy specifically, I have three normal (or what passes for normal) cats. Every night I call them in for dinner and curfew. If they don't all come in right away, which honestly 95% of the time they are within 5 feet of the door waiting for me to call or yelling at me if I was late calling, I hang out outside calling while I read a book or take the tracker and look. Rocket and Fury will follow me from inside the house; I think because they don't get dinner until all three are in. Link though will do the same piling of toys at doorways. Link also piles toys at doors or windows during the night. The whole point is that the toy at the doorway may be less of an offering and more of a teddy bear/security blanket/comfort thing. Maybe that mindset will help some; also if she likes to hold a specific toy get multiples of it so she can have security blankets in different places.
More of a random thought, when she seems to be in attack mode. Instead of diffusing her maybe try to roll with it and safely redirect her? Valerian root and catnip toys can trigger an energy release and decompression with my guys. I know when Link is in a mood and nothing else is working I can toss a catnip toy and he will kick it a few times then go mellow. Rocket does better with the mix of the two because she doesn't react as strongly to just catnip. I personally love this one Purple Haze Tickle Pickle because it is well made, has held up to my cats for a year and still smells strong.
To the crying if outside and toy specifically, I have three normal (or what passes for normal) cats. Every night I call them in for dinner and curfew. If they don't all come in right away, which honestly 95% of the time they are within 5 feet of the door waiting for me to call or yelling at me if I was late calling, I hang out outside calling while I read a book or take the tracker and look. Rocket and Fury will follow me from inside the house; I think because they don't get dinner until all three are in. Link though will do the same piling of toys at doorways. Link also piles toys at doors or windows during the night. The whole point is that the toy at the doorway may be less of an offering and more of a teddy bear/security blanket/comfort thing. Maybe that mindset will help some; also if she likes to hold a specific toy get multiples of it so she can have security blankets in different places.
More of a random thought, when she seems to be in attack mode. Instead of diffusing her maybe try to roll with it and safely redirect her? Valerian root and catnip toys can trigger an energy release and decompression with my guys. I know when Link is in a mood and nothing else is working I can toss a catnip toy and he will kick it a few times then go mellow. Rocket does better with the mix of the two because she doesn't react as strongly to just catnip. I personally love this one Purple Haze Tickle Pickle because it is well made, has held up to my cats for a year and still smells strong.