I broke my screen door handle, and replaced it with something a bit more heavy duty. The "inside" part should allow the latch to work. I don't have a latch on mine, so if it needs modification please comment.
For a nice print set your supports to: 20% grid
Fusion 360 and Calipers
I use Fusion 360 from Autodesk to make the design, and a set of digital calipers to take all the measurements.