Looking for right door strike plate

I noticed the corners were soft and so I dug in. I chiseled away all the soft wood, now what? I was planning to cut a few pieces of scrap wood and glue it to concrete, calk the gaps on the frame. How do I patch the door? Is there a product that could fill all that volume?

I recently had to replace a pocket door latch because the old one broke. I found the exact replacement. I've replaced these before without issue. But now I have a problem. The latch is held in place by 4 screws. There is not enough wood behind one of the screws for the screw to gain purchase. (In other words, I have a screw loose.) It is circled in red in the first photo. The screw hole is circled in the second photo. You can see light coming through the screw hole. This is a problem because the inability to tighten that one screw causes the metal plate not to be tight against the door, so it rubs against the inside of the pocket door slot and gets stuck. I've tried various plastic screw hole menders & wall anchors and none of them work; the screw remains loose. I'd be grateful for any ideas.