I have owned and been driving a VW
Golf TDI since 2011 so here are some observations about the car. The Jetta TDI should be fairly similar so I think this post will give you a good idea.
First and foremost, after 4 years and 50000 miles I now get 45-50mpg. My daily commute is 40 miles each way (80 total) and it is 70% highway 30% city. But be aware that a TDI engine takes about 50000 miles to reach its peak efficiency. So you will probably start at 35-40mpg and gradually see the economy improve.
The turbo kicks in at 1950rpm and on the highway, on 6th gear, 65mph is just over 1800rpm and 70mph is just over 1900rpm. Keep the turbo off and the mpg will stay high.
I am also reasonably puzzled by some people claiming a manual gearbox is not for this car. On the highway, cruising at 70mph on 6th gear, it makes no difference whether it's manual or DSG, although the DSG carries about 80 more lbs of weight.
The manual gearbox is, I believe, a very personal choice and depends on your driving style. I make use of that extra control of my car 110% when driving and I wouldn't have it any other way. FYI, I test drove the TDI with DSG and before that, I owned the 2.5 VW
Rabbit with an automatic (not DSG) gearbox. I just hated it. Nothing like the ability to cut in slower traffic, downshifting from 6th to 2nd going from 70mph to 30mph, without even touching the brakes! The clutch is a bit on the harder side but again, I prefer it that way. But back to topic, the DSG was amazing when accelerating but when slowing down it felt like it would just go to neutral and let the car roll. So to summarize, Golf TDI plus manual gearbox is the way to go!
Some additional remarks about the car: I live in Montreal and in the winter my car stays outside while I'm at work, at temperatures as low as -30C. Never had a problem with the cold weather. Over 4 years, the only issue I had was some problem with the intercooler, that was repaired under warranty. service at the dealership is quite expensive at around $400 per year, but now that the warranty has expired, I will take it to a cheaper shop. And finally, at 6'3, if I push the seat all the way back and all the way down, my feet don't even reach the pedals and my head is about 5 inches from the ceiling. So it's fine for taller drivers.
I can't tell if for the OP's case a TDI would be the right choice and I can't compare it to other cars that I have not driven, but I hope this was some helpful information.
I'd rather die peacefully in my sleep, like my grandfather, not terrified and screaming, like his passengers