Tuning a motor usually requires several sets of plugs, the cost of plugs is relatively cheap compared to the cost of hiring a tuner. I'm proud of you, you have gained the knowledge and confidence to do it yourself! My only charge is that you pass it on to others so they too can learn and have fun!

The gap won't change the heat range of the plug, that's determined by the porcelain inside the plug and how fast it transfers the heat to the plug base, usually shorter porcelain is a cooler plug. The strap and threads on your plug show too much heat, performance will benefit from a cooler plug.

Set plug gap at .035, usually high performance motors like a tighter gap (even with HEI). 36° total timing is ok if the motor likes it (some head designs don't), 2° can make a difference as long as it doesn't ping.

Ignore all the tuning specs on the radiator, those are factory recommendations and you are way beyond that now. Keep a log of all changes and their results for future references.

AND most of all, ENJOY!!