Dave,

https://www.flickr.com/photos/126231...n/photostream/

I cleaned out all the rot wood, replaced it with treated deck wood
that presumably won't rot.

Treated wood will still rot, it just takes longer. There are also different
ratings for pressure treated lumber. Typical deck lumber has less
protection than wood labeled "safe for ground contact". Usually the better
ground contact lumber has a series of holes where the chemicals are forced
deep into the wood.

Also, pressure treatment usually doesn't penetrate that far into the wood.
If you cut the board, the center section is usually untreated wood that
would need to be painted with preservatives to minimize rot.

the base of the treated wood now lies on about a 1 inch
buildup of qwikcrete - that should stop much wicking.

Unfortunately, concrete does not stop moisture. That's why plastic vapor
barriers are placed under concrete slabs. Without some kind of barrier
between the concrete and wood, you can potentially still get wicking.
Granted, the PT lumber will probably last longer.

what to do next? I'm not going to put in any plain trim
and have it rot out again.

If you're going to continue with the patch job, I would pick up some PVC or
composite lumber to use for the trim. It's basically plastic, so it can't
rot. It mills and paints just like wood.

I agree with DPB though, the door is installed incorrectly. The door sill
is sitting below the level of the walkway outside. You may be able seal it
off temporarily, but at some point water is going to find it's way under
the door sill (there is usually wood under that metal covering on the door
sill). It would be smart to either raise the door frame, or lower the
sidewalk. I'm betting it would be easier to raise the door frame.

As I mentioned previously, you would be better off to order a new composite
door frame and stop messing around with patches that may or may not last. I
replaced my door frames in about 2-3 hours each. Remove the door from the
hinges, remove any interior trim, cut the exterior caulking with a knife,
cut the nails with a reciprocating saw, and pop out the old frame. Then
it's a simple job to install the new frame.

Best wishes with your repair!

Anthony Watson
www.mountainsoftware.com
www.watsondiy.com