You're on the right track!
I can't find fault in your choices except that PHP may not sell you a 120HP tune for your truck. This is due to the connecting rods used in the later 7.3L engines that aren't nearly as robust as the previous design/materials.
I don't know if I would have such a large gap in tunes (25 to 80HP) either. I tow a lot with my truck and a 40-ish horsepower tune is going to work better than the 25. I'm not saying that there's no use for a 25 HP tune, but I usually gross in the 15-20K range and tunes in the 40 HP area work well for me.
In all, I would recommend 40 and 80. The 100 would also be a good choice for those "legally sanctioned" events that don't occur on public roadways.
My friend has a 99.5 6-speed truck and really only uses a 100-ish HP tune. It's the only one he wants to drive with because it's responsive (not touchy) and has great driveability. Out of the entire library of tunes I have developed for it, he only uses two. When towing, he's in the 50 HP range but he doesn't gross more than about 11K at any time.
You're going to have to worry about turbo surge once you tune it and start pulling though....so a turbocharger upgrade or part upgrade is going to be in order. Also, I have noticed that the 02-03 trucks seem to get weak High Pressure Oil Pumps long before the earlier trucks (lower attainable pressure at a lower mileage/age). That may become a concern in the higher-HP tunes as well.
Bill has GREAT tunes that work well on manual trucks as far as pedal feel and response go. They're not touchy but you can definitely feel a difference.