Don't be frightened to try those meals that you have no idea about, you're doing the right thing by under estimating the carbs, you can then correct afterwards, and make a note so next time you can get it (more!) right - you can then enjoy the meal even more.
Always test and have quick acting carbs at hand just in case - but you can at least learn by a mistake either way.
As for extended blousing - I don't pump so can't help but as above, testing and trial and error you'll get there.