Good idea on the incubator, I made the mistake of waiting to the last minute hoping she would lay later on then expected, but laid sooner.
1. I don't know how you have your tubs set up in the room, but I never liked just having a tub out in the open with all sides exposed. Try stacking them and putting a towel over them giving it a rack feel only having the front exposed to the room. This will make the whole enclosure act as a hide and give them comfort, although some do prefer a hide and feed better as a result. SOMETIMES. I have 2 snakes right now that do this. If you notice them going off feed put it back in until breeding time. Then remove and let them do their thing.
2. They will be fine in terms of being stressed. I usually only leave my male in with a female for 2 days at a time, and then let him have a day or two to relax. With my boy though, he's a breeding machine and doesn't ever take meals in between and just cruises his cage until I put him in with a girl. Be careful with overbred males as they can lose weight quickly which can lead to a decline in health with the animal.
3. I personally add the male to female. I'm pretty sure most do this too. Easier to keep track of too if you have a larger breeding project. Usually in a rack the male will go down a tier every couple of days until he reaches the bottom. And repeats this until ovulation is witness or when female shows no sign of wanting to breed.
Good luck with breeding, this is actually my first season and I'm having a blast! Its like christmas all over again. Wait till you get the itch even more and start collecting morphs lol