What you are concerned with using dynamic timing is the max timing you end up with. Is your dist done advancing at 1500rpm? Check again at a higher RPM and adjust to your max advance spec. If at idle the timing is advanced of the spec it seems to me that would indicates weak or missing/broken advance springs, located in the dist under the points plate. But I doubt that would be causing a hot floor pan from an overheated exhaust - sounds more like an exhaust leak or perhaps excessive idling. Once you are rolling down the road there may be enough airflow under the car to cool things down.

Hope this helps,

Joe in St Louis