Backspace in Evernote does not delete words at an even speed
The backspace key
The backspace keep repeated action is controlled at application level, either by the keyboard App, the Evernote App or the Android System.
AFAIK, there's no setting to control the spead of the action repeat cycle.
The undo feature
A premium user of Evernote has a backup privilege that creates a snapshot of every note on the Evernote server every 8 hours.
HELP: Need to restore text deleted from a note

Note history creates a snapshot of your not on our server every 8 hours.

Aside from that, there's no undo capabilities on the application.

Note: As already suggested on the comments under your question, you could submit a feature request to have a Redo functionality.