Your Ram 2500 will handle that 12.5K lb FW with 2500 lbs of hitch weight, but you may get some squat in the rear that may require aftermarket airbags if you do not have the OEM bag leveling option. Since your truck has rear coils, you have fewer options on how to help those coils under heavy loads - I think this is the biggest worry by others that have posted.
When traveling, remember that your stock FW tires will most likely be limited to 65 mph. Once you get to the west coast, you will be limited to 55 mph due to legal speed limits on towed vehicles. You will also find your mileage drops based on your speed since you will have much more drag pulling that FW. Give yourself more time than needed to make the trip and you will be able to enjoy the extra buffered time instead of having to chase the clock or calendar to make a destination.
I compute my driving time with stops at 50 mph and will not drive more than 500 miles each day. This makes a 10 hour driving day that works for me and keeps me sharp and fresh. Only you can set what is comfortable for you you, but at least this gives you a baseline from someone that has RV'ed for number years yet is not a professional driver by trade and still works full time.