I have not had a child go through the surgery, but I had my tonsils out 2 years ago. Yes, it hurts- but I am SOOOOO glad I had it done! It tok me about 3 weeks to recover, but I hear that kids heal faster. I have an almost 4 year old, so I will try to answer your questions as if he was about to have the surgery done.
1) Tell him that the reason he keeps feeling sick is that there is a broken part, and the Dr is going to fix it. He doesn't need to know it's being cut out.
2) Okay- like I said, I took about 3 weeks (6 to total recovery), but I hear kids heal faster. I was NO GOOD to anyone the first week. Thankfully, my hubby had taken that week off of work to care for our son. I might consider taking that first week off for him- unless it's a grandma/Aunty caring for him while you work. They will be as attentive as you would while he recovers.
3) My hubby broght a magazine with him. The surgery is REALLY quick. (like 20-30 minutes) I think for my child, I would bring his "Buddy" (favorite teddy bear) to help him feel safe- BUT, make sure the hospital will allow it!
4) I woke up with a WHOPPER of a head ache! I get migrains, and this was darn close to one in regards to amount of pain, but not in the same trigger spot as my migranes. I think I would ask that they does him with an IV pain reliever before they wake him. If I were a child, the head ache would have brought me to tears- and crying would have made it worse.
**Also, I see you have a 5 month old: please, do yourself a favor and let someone watch her for the day while you tend to your son. She will sense your stress while at the hospital and will make it harder for you. For that day, your son needs you 100%.