Adding a pyrometer to be able to see the exhaust temps is helpful, but they shouldn't be a concern with a stock or basically stock engine -- it's when you get into adding a lot more fuel that it becomes a concern. It's the heat coming out the exhaust ports, going thru the manifold & into the turbocharger that spins it up even more than the exhaust flow -- when you add more fuel you're going to get more heat & with it more boost, until the wastegate opens to limit how high it will go.
For your purposes I'd do the same thing I did to my '98 2500 4x4 24-valve Cummins, which I bought to do a lot of heavy load carrying & towing with -- first thing was to make the engine "breathe" better, with a K&N air filter & a free-flowing straight-thru muffler. Mine has the 100% failure rate Bosch VP44 injector pump which Dodge quit using after 2001 & I just got the newest Freightliner upgrade version, which gives the engine 22 more HP & a little better fuel mileage too. And that's all the farther I'll go at least for a while -- no aftermarket tuner, chip, "hot rod pump", etc. I don't need to win drag races & I intend to keep this truck forever, so while I like the power increase I've already got, longevity & durability is more important than tire-smoking HP & I'd bet you're the same way.
I've pulled loaded trailers from here in NC out thru Colorado & Wyoming to the Bonneville salt flats & back (4000-mile round trip) & the worst fuel mileage I ever got on those trips was 15.6 mpg, with the old stock injector pump -- should get 2-3 more mpg now. I did recently add an Edge boost elbow which allows the turbo boost to come up quicker & go a bit higher than stock, but it's not a major modification & won't effect the longevity of the engine. And with those few modifications I have no trouble pulling trailers or carrying a lot of weight in the bed -- I've had 3500 lbs of stone in the bed & was pulling my 16' tandem axle utility trailer with John Deere diesel tractor & implements too -- with the cruise control on & the speed never varied more than 1 mph.
Only problem I can think of that others have talked about but I haven't had is with the automatic transmission -- people have said they don't hold up well if you're towing all the time. But I've got about 150,000 miles on mine & the only problem I've had with it is an electrical glitch that made the lock-up torque converter lock up then unlock, lock up again then unlock, over & over. But there was a service bulletin on that years ago (voltage fluctuation) & I haven't had that problem since.
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