This is probably it. I didn't sit down to a meal that was less than 90 minutes long, and that's a little short by Italian standards at a restaurant. I drank a lot of house wine, which often doesn't ever get bottled and corked, so I also wonder if there's something present/absent from aging a little less, or potentially from oxidation when it sits in the restaurant's cask. I'll take it, though, most of the time two drinks of anything gives me a headache the next day.

For the thread - house wine is a good option in many restaurants. Sometimes it's from a cask in a carafe, other times it's a private label bottle, other times it's just a house-recommended commercial bottle. It will generally be inexpensive, but if price is a factor, ask. Case in point, I had a meal last week with an excellent house Vermentino - private labeled. It was 22 euro a bottle. Worth it, but if you expect 8-10 euro per liter, it's obviously a little more.

That aside, at least in the price range of wines I drink (which is generally on the inexpensive side), a markup of 2x retail is my rule of thumb in Italy if it's in a bottle. That might vary from city to city, would love to see other data points.