I'm unclear as to how to read this report exactly. What does the column with the green bar refer to? What does the green and grey dot column refer to?

I believe the column refers to the colour of the nation you attacked / were attacked by. In this case, you attacked / were attacked by a green nation.

The green and grey dots refer to whether or not (respectively) the attack destroyed its target.

So a green marker when I am attacked means the unit survived, grey means my unit was destroyed?

I believe green means the unit was destroyed, regardless of you're attacking or being attacked.

You could always check to see if your units are still there.