Daniel,
On your water leak some ideas.
1) If you are loosing 1/2 a radiator of fluid in a 2-5 hours of driving you have some major leak. So likely water pump seal, heater core, head gasket, or unlikely but possible a cavitation hole leaking coolant into a cylinder when the engine is hot and running. (Could be a hose.)
a) You may want to buy or see if your local auto parts store will loan a radiator pressure tester. But only pump up to 13-14 psi (What the cap is rated for.) so you do not create a new problem. I would suggest you do so running as you may have a head gasket leak and you do not want to hydro lock your engine. If leaking externally you should be able to see something leaking under pressure. It could be your truck only leaks when its running, hot, and the cooling system is under pressure.
b) Buy some radiator test strips to see if they flag exhaust gasses/material in your coolant. Sign you likely have a head gasket issue or possible but not likely a cavitation hole in one cylinder.
2) Less common and harder to find leaks you may want to look for.
a) Water pump weep hole. Often these leak on and off till the seal fails. See if your radiator fan has play, sign the bearings are going out and taking the seal with them. But can leak before bearings wear out. (Use a mirror and flashlight the hole will be rusted or you will see coolant marks or dripping.)
c) Oil cooler. When mine leaked I just found coolant coming out of the oil pan (Usually last) when changing oil, it did not mix and milk up.
d) The radiator core. Look for wetness or streaks of dried coolant.
e) Head gaskets. As mentioned above you can buy test kits.
f) A bad freeze plug, engine block heater, thermostat gasket, or other plug/sensor.
g) Leaking radiator overflow container. Coolant expands and goes into the container where it leaks out and cannot be pulled back into the radiator. (But this would not happen with a 2-5 hour drive.)
3) Also you originally mentioned you had concerns it may be too hot or overheating. So think about perhaps just replacing the thermostat, radiator cap, up and lower radiator hoses for good measure and that will take out some of the possible leaks as well. (ALWAYS USE A MOTORCRAFT THERMOSTAT!) Then perhaps test your radiator for flow by filling up and draining via the bottom radiator hose outlet. If it comes out fast and free (Radiator cap off.) you likely have a good radiator. If slow or restricted you may have a compromised radiator.
Keep watching, you will eventually see a leak or notice steam or odd colored smoke out of the exhaust.
Good luck and let us know what you find.