Water seepage under front steps

We have a closet / alcove in our basement that is directly under the concrete front porch area. While removing some inulation to correct a bad installation by the builder getting ready to install bead board on the ceiling, I noticed a leak has developed under the concrete at one of the corners of the porch and the plywood has started to rot.
The porch area is approximately 10 feet wide and there is an 6 foot wide section that goes to the front door. The leak is right at this outside corner of the bricks that goes from the front of the house up to the front door. It might help to note that the porch is approximately 18" above ground so I don't think the leak is not coming in from the side ir at ground level.
I have noticed that water pools at this corner during heavy rains (I guess it's not sloped properly to shed the rain), but there appeared to be no leakage in the area below when I had checked in the past.
The seam between the concrete and brick seems to be tight.
The plywood that the concrete was poured on is starting to rot out only at this corner. The framing is all 2X4 around the entire perimeter and the "joists" which are 12-15" on center in between. Plywood and framing are not pressure treated. The perimiter boards appear to be nailed in with masonry nails every couple of feet, not anything that would resemble the attachment of a ledger board that would meet code.
Questions:
1. What would be the best way to repair the leak. Here are some thoughts I have: A. Run a bead of concrete caulk at the brick to concrete seam around the perimeter of the porch area. B. Chisel out the joint between the brick and concrete and put a repair patch that angles the water away from the brick.
2. What do I need to do about the plywood where it has started to rot out. My assumption is the framing was needed to pour the concrete, but is not structural support now as the concrete should have rebar. If I am wrong in my understanding of the need for this framing and the plywood is needed, how should I repair the plywood?
Any help would be greatly appreciated.
David
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