The 4231 I use for a weather cam will hold color all night if I "force" it. It's a fine picture for a still, but because of the gain required motion tends to get blurry. I use a utility that switches all of my Dahua cameras at once to night or day mode as appropriate. I do see lightning as flashes of light, IE much brighter picture, but it doesn't blind them. Having most of them looking, more or less, downward may be a factor as well.
Getting really fast response for automatic dynamic range is expensive. Keeping it locked in to IR is probably the best solution. I haven't seen any camera, other than high end stuff, do a lot better than the "prosumer" stuff we use.
Switching from 3mp to 2mp won't help night vision. The size of each element on the lens is the key and what, how much light, comes through the lens. From what I can gather about reducing resolution, it is an electronic compression of the original size image. I could be wrong on that, but that's what I have gathered from watching a lot of video comparisons ad nauseum.
I recently saw a guy complaining that his video camera was "junk" because he could get a much better picture with his DSLR. All he needs is a video camera with a $100, or more, lens and a 1" or bigger sensor, oh yeah and IPC65 or better waterproofing and a really large drive array to store all that imagery.