Hoping and praying for you guys, esp Brittany. The chemo does have a tendency to upset the tummy more, the further you go along. When my sister was doing hers, they'd go 6 weeks at a time, then take a break for 4, take some pictures, and do 6 more weeks, etc. She'd do hers on a Friday afternoon after school, and then spend the weekend recuperating. I don't remember how many rounds she did like that (3??), but she hasn't had to do anymore since (over a year now).
Two hours is a long haul, and then to have to get stuck 4 different times before getting a good "tap"... man, that'd stress me enough right there to put me on the nauseated side of things all by itself. wishing you well. Try be sure Brittany is fully hydrated next time she goes, and hopefully that'll make a difference on the "stick".
"There but for the grace of God, go I."
"... His mercy endureth for ever."