Yes, you can seal those interior holes. You should also check the slotted holes outside (called weepholes) to ensure they are not blocked with debris. Dust, leaves, twigs, bugs, etc. If they are clogged, that could lead to water backing up into the interior.

Thanks for the welcome. Yes we have, and we also had a couple of local handyman/contractor people look at it. The thought is the frame is a permanent part of the the building. They gave us some crazy numbers in my opinion. My thoughts were it couldnt be but so hard to just replace the door alone, till I got to looking at doors lol.

I have the same set up in my garage. I went to our local building supply salvage yard and bought a really nice fiberglas exterior blank, not punched, not mortised. I did a trim job on the width to make it fit the steel opening, mortised where the framed hinges were, then punched it where the lockset was on the steel frame (which is definitely not the same as a wooden prehung). The fiberglas will outlast both wood and some metal doors, it is paintable and workable, as in trimming. Adding metal to a wood door is not a good idea.