I am certain I have over killed the replacement stepper motor.(1600 oz. in)
I wouldn't count on it. Especially if you're using a gear reduction with it. My guess is that the gear reduction may have been the problem in the first place.
A gear reduction on a direct drive acme screw will often reduce performance, as the steppers lost torque as rpm's increase. The reduction is making it spin 2-3 times faster, and could actually be reducing your torque.
A 1600 oz motor is serious overkill for that application, and that's generally a bad thing. I've seen a lot of people buying those motors lately, and in most cases they perform worse than properly sized motors. The main reason is that they tend to have very high inductance, which causes the torque to drop off very rapidly.
It want to increase the resolution a little more than on the previous and just want to be sure I have enough power
Are you adjusting the microstepping to change resolution. Reducing microstepping can cause motors to run rougher and suffer from resonance, which can lead to lost steps.
What kind of drives are you using, and what voltage are you running at?
Is that a 5 start acme screw? If it is, I'd try running it 1:1, with the microstepping set to 1/8 or higher, and see if you get better performance.