I finally read through this whole thing after several attempts.
I wonder if one could try a much simpler/crude attempt at increased EGR. insert a length of 1/4" copper tube into your tail pipe (or drill a hole in your muffler and insert there) and bend it to run it under the car towards the engine. This will serve as your "EGR cooler" as air rushes past the copper tube. At the end of the copper tube install a hose that goes to a ball valve (to adjust/turn on/off) and then to a small vacuum port on the manifold. If it runs ok, advance to larger vacuum ports and adjust the ball valve as required.
No? Just a thought. It might be fun to try. Less investment of time and money.