Oh Heather, I'm so sorry. It sounds like classic colic, given the hour of the day and the duration of the crying. Gil was the same way. It was so hard!
Does Kali have reflux? I know that added to Gil's problems. There is also silent reflux, where they're not spitting up, but their throat is burning with stomach acid. Does she ever arch her back during/after a feeding? This is classic for reflux.
It could also be the formula. Milk intolerance is a possibility. What kind of formula are you using? Are you using the powdered? With Gil we weren't able to use the powdered kind until 6 months because it was too thin/watery and his stomach sphincter couldn't keep it in his stomach. We had to use the ready to feed kind.
As far as dealing with symtoms (whatever the cause)...
What really helped us was having a list of "comfort measures" posted somewhere, and we would just go down the list until something worked. Swing, bouncy seat, walking around and around (DH wore treads in the carpet!), pacifier, white noise (a life saver) - fan, running water, music machine, vacuum when really desperate. There's the "Happiest Baby on the Block" techniques too - swaddle, a loud shhhhhh, swinging motion, sucking on a paci, and holding her on her side (although this might exacerbate reflux).
It definitely could be overtired. I know some babies just melt down at the end of the day from stimulation (not necessarily even OVER stimulation, just getting used to life kind of stuff).
Hours and hours of a crying baby is SOOOOO hard. Just make sure you get a break from it too. It can be overwhelming. I know I had many nights when I just broke down from it all. It gets better. For Gil, it was like a switch went off and he just got better and better. Of course, he still has his moments

but the colic thing was the WORST! Have you talked to your pediatrician about it to get his/her input?