P.P.
For one thing, don't mix formula with breast milk. It's not recommended. It should be one or the other, preferably when problems like this come up, it's best to use breast milk.
My youngest was a screamer but for her, I believe in the end it had to do with her IQ level and the fact she was bored. Nothing held her attention until we began buying toys that were above her current learning curve of age. I'm not talking dangerous toys but advanced learning toys.
Once we removed the boredom factor, the screaming stopped. This child could read, knew colors, shapes, and numbers, as well as the ability to compute simple math all before her 2nd birthday. She is heading to the 8th grade in the fall yet she is still 2-3 grade levels ahead of her classmates and always has been even since kindergarten. She's a straight A student, always has been, and she is in the Junior Honor Society, advanced math, etc...
In the end it all came down to boredom and keeping her occupied. It had nothing to do with food or being hungry although she had a healthy appetite and yes, I did breast feed her, but when she wasn't napping or eating, she was engaged in educational play. It stopped the screaming in its tracks.