It sounds like you are really putting too much of the equipment on you. If you want to pull the whole way share some of the load, and try to use just bottles and jersey pockets/saddle bags to carry stuff. The heat from wearing a back pack is not great in my opinion. Surely some of the guys with you can carry an extra tube and such. Also, I will likely carry 2 tubes for myself, if I have a blow out I might get a replacement one at the next rest stop you come to (bring cash). I actually had to buy a helmet at one of the more equipped rest stops after my nephew cracked his!