Expected Performance While Towing?

[opiefire]

My truck is a 2500 CTD HO QC LB 3.73 with a 48 RE. I have recently purchased a 2002 fleetwood triumph 33 1/2 5'er. I bought it from a family member, however I won't be picking it up until April. I recently installed all my gauges( EGT, Tranny Temp, Boost). I have the AFE torque tube and the rest is stock. The GVWR of the 5'er is 13,700 lbs, and the hitch weight is 2212 lbs. The dry weight or the 5'er is 10,325 lbs. I have owned rv's in the past (but not this large) and am aware of how easy it is to over load (which I aready am). I am concerned about already being over the maximum weight limit. By my estimate I am 3100 lbs over weight (given 400 lbs for occupants and honda eu3000is) Does anyone have a similar setup? I live in the Idaho, and I wonder:
#1) What speeds can I expect while pulling 5 to 6 percent grades?
#2)Will I be able to set the cruise on 68 mph the interstate, and will my truck maintain it?
#3) Would the Edge EZ 40 to 70 HP box help me while towing?

I know my truck can tow this, but I also don't want to get so over weigh that I am extremely unsafe. I have read multiple posts that discuss the repercussions of being overloaded, and it scares me. I don't want to get to the top of the hill the fastest, but I also don't want to hold up traffic going 35 mph up the hill. I value all opions, and appreciate your input.