I tried to develop my PCB but it failed.

After 1 hour of exposure, I used the "developer" from MG Chemicals to develop the board. my developer mix consists of about 10 parts of water to 1 part od developer.

At first I thought I was very successful, because in about two minutes, 1/2 the board developed perfectly. Now the 2nd half was struggling. I left the entire board in the developer because I wanted it all developed. After it appeared that it all was developed, I noticed that some small track segments completely disappeared. The board is not recoverable to me.

So I have two questions.

1. I want to rearrange the circuit and I want to understand why an 8051 chip has such a weird configuration (like A15 in the top-dead center instead of the outside of the chip). and how are we supposed to work with the "Jedec" standards?

2. What is the absolute maximum width (in millimeters) that I can use for a track between any two pins of a standard DIP IC, if I make the tracks on the solder side of the board?