Photos of doorway

Because i mentioned the windows

....but they added decorative edging!

Holy close ups. You need to back up and take a full picture but for starters there appears to be no door sill. The repair is to pull the unit and install a sill and reinstall or since that looks like a run of the mill steel door buy a new prehung unit and swap them out. Since your picture is so close up it makes it almost impossible to get the full picture of what is going on this is only an educated guess at this point. And from the looks of it the jambs were not procured with the proper jamb depth and they jury rigged extension jambs from plywood instead of pine trim.

If you buy and properly install an exterior pre-hung door it will have the seals around the sides and top, and an adjustable threshold at the bottom to allow for the gap.

You can also remove and rebuild the frame yourself, buy a new threshold and seals, and hang the existing door in the frame you build. However, based on your question it does appear you have done this type of work before.

Bruce

Thank you all!

Sorry about the photos, thought they'd be more useful then from farther away, my bad.

As for just replacing the door - that seems like a pretty extreme angle on the floor where it connects to outside - will a prehung door be able to handle that?

And no, have not done this kind of work before, I'm pretty good at picking up things with my hands, but simpler is definitely better!

Here's the wider shots.