I would suggest that you take a read through Aiko Nanoko’s Thesis on the UWG (see pdf at bottom of the page) before setting your sensitivity study to run. Aiko has done a sensitivity study of a few different parameters to see which ones had the largest effect on cooling energy use. It may help you narrow down your list since some of your parameters won’t have a significant effect on UHI. You have also left out two parameters that have a significant effect (the sensible heat from traffic and the fraction of building cooling energy that is rejected to the urban canyon).
Also, rotating the urban grid won’t have any impact on the Urban Weather Generator’s calculation since the UWG tries to approximate the average change in air temperature over a district’s urban canyons. It does this by computing the energy balance of an omni-directional infinite urban canyon.
Rotating the canyons may affect the radiant temperature differences that you will get in different parts of urban area but it will not affect this average urban canyon temperature.