1. The number of quarts is directly proportional to the area added with the cooler. Put in half a quart and run the engine. Let it sit and read the stick. Add as required.
2. The type of pump should be dictated by the engine, not the
oil pan. If you are running higher RPMs and need more
oil to protect the engine, by all means, add the HVHP pump.
3.
Oil that is too cool is not necessarily a good thing. You may want a thermal valve that opens when the oil reaches a certain tamperature, like 200 degrees ( or whatever ).
Just my $0.02