I think the issue isn't in the UV here; so unwrapping everything again won't solve it. As toedar23 said it's probably the face normal that are probably messed up.
This is completely solved in 2020. There is a new 'mode 5' which runs in the background and significantly speeds everything up. This command panel issue was known to the devs and it's been resolved.
I would look into Maxscript to solve this. You could look at this script as an example, and expand upon it if needed. http://www.scriptspot.com/3ds-max/scripts/max-defaults
In the FFD Parameters, try changing Deform to "All Vertices". If this solves it, it's because you've started with a planar mesh, so there was zero depth on Z for the FFD volume to grab with.
about the light leaking through,would this happen because the light isnt casting shadows? if so,then wouldnt the problem be solved simply by using shadow casting lights.