Were your old shifters Shimano flat bar road shifters like the R440 style? They would have had more than 3 positions to allow for trim and they would have worked with a road type front derailleur. Shimano MTB shifters have only 3 positions but pull more cable so as to work with MTB front derailleurs.
If you have a road front derailleur and MTB shifters, this would account for the "too much throw" problem.
I may be wrong but this explaination fits with all of your symptoms.