I run 32s at 70psi. I weigh 142 and the bike weighs 40. Current tires/tyres are the stock ones on my Allant - Bontrager H2 with reflective sidewalls. I've gotten four flats in 1800 miles, one of which caused by a nail and another caused by a small piece of gravel penetrating the tread and just barely scraping the tube.

I think that the wheels and the bike itself make much more difference in speed than the tires do.

Tread does make a difference in speed, but if you're on roads and paved MUPs, it will make almost no difference in the wet; it's more for going off the road. Hybrid tread is good for fine gravel paths. Slicks are fine for the road, dry or wet.