If you can not get Lacerte to work it out to your satisfaction, do an override as Home Mortgage Interest (code 21)

Check the box at the bottom of Screen 25, so Lacerte ONLY does a worksheet. 

Sometimes you spend more time trying to get the software to behave then you do just giving a correct number as an override. The worksheet does not go with the return, regardless of what method you use. OUR goal is a correct return, with or without the help of the software.