How do I get the space between rows 2 and 3 to be the same as the space between rows 1 and 2?
So I just want to move row 3, NOT row 2.

If you use align and distribute, there are selections for first selected, last, etc. There's also an option to put equal spacing between rows.

I don't think there's an easy way to achieve what you want. The align and distribute dialog can certainly put equal spacing between rows, but it assumes that the first and last items are in the right place, so will move the ones in-between to adjust the spacing. There are more convoluted and manual approaches that could do the job, using some temporary construction lines and snapping, but no simple automated method I can think of.