You could attach 24" of hardware cloth like an 'apron' around the perimeter base and fan it out. (screw on with washers, or use pneumatic staples; really strong, 1" ones)Oh ok and how would i keep predators from digging their way from under? Its a dirt floor
You scrape away a few inches of soil, lay out the cloth (attached to the well house base), secure with 12" garden staples, and cover with the dirt and some gravel if needed.
Go all of the way around.
The door should fit very well, or frame it in behind, so there are no open gaps.