1 the simple belgian bootie type overshoes give a bit of warmth and keep mud off the shoes, but if it's really cold/wet, full-on overshoes are better (you'll still get wet feet, but they'll stay warmer)
2 short answer...
bring a pump
the only time i've used pitstop, the result was simply to spray foamed latex out of the puncture, even after several tries, inject, cover the hole to allow it to set, repeat, repeat etc., accept defeat, give up and fit emegency spare (a preglued lightweight tufo)
*if* it seals the hole, it'll inflate the tyre, i think it's 90psi max, you could top up with a pump, but with higher pressure it might increase the chance of blowing out the latex plugging the hole
fwiw now i carry tufo extreme, this doesn't inflate, but from what i've read is more likely to be effective, however i've not had to use it yet and will be quite happy to carry on that way!
really long answer...
read the tub threads anchored to the top of the listings
3 you put chamois cream on the areas that will be bearing the weight and/or rubbing on the pad, you can also put some on the pad, especially if it's going to be a long hot ride
i use the assos one, it's not oil based, main ingredient is water, it washes out easily