what are the pixel dimentions of the images?
What bit rates do you set in ME?
Regarding setting AE ram to 58gb, i believe its best practice to leave 10gb+ for the system to use other wise it may slow everything down.
The ram usage shown in AE is dependant on whats in the comp I think so its possible it simply cant use any more, doesnt need to.
I no expert im afraid, so take my words with a pinch of salt!
I have had many seemingly simple renders take more than a day.