First off - what a great viz! i love the Waterfall in between the bars for Now.
This post was from a few weeks ago. Did you find a solution to the issue? I found that the axis for the dual axis are not 'synced' and that forcing the axis to Sync will result in - what I believe is the correct view. You can see in the screen shot that you attached - the right axis is 0-3 rather than matching the left axis of -13. Syncing the axis fixes the issue.
Tableau 9.3 workbook attached with the axis synced.
I hope this helps you or others.
Waterfall - Tableau_PV.twbx 1.0 MB