Non-resident returns and NR4 slips

I've found a few useful posts about this topic but am still unclear on a few points.

 

I have NR4 slips related to dividend income from a Canadian institution.  I recognize that for my non-resident return I'm supposed to use the total income from all such slips like this in completing the Statement of World Income. 

 

Two questions about this:

 

1. The world income asked for 'net investment income'.  Is this meant to be the amount after withholding taxes (i.e. from the NR4 box 16 'gross income' minus box 17 'non-resident tax withheld')?  Or is it just box 16 (gross)?

 

2. From what I've understood I'm also supposed to enter these in the T-slip section (i.e. in addition to using the values for the world income statement).  I read already that there's no NR4 option in TurboTax, so I could use T5, but the boxes numbers are different.  Am I supposed to do this, or is it double-counting?  As far as I understood the withholding tax is your final obligation to the CRA.  And if I otherwise didn't have to file (as was the case the past few years) I wouldn't have done this anyway.

 

Hope this makes sense.