Hi DR,
Well, I did a quick google of 'galactic day' since I'd never heard of such and one web site says there is no such thing and another says it is a term that came from a Star Wars movie. You'll have to go with what you believe to be the truth, but no, none of your response finds itself in agreement with what I wrote so I don't know why you started off saying that you agree.
As far as the plants and trees needing a true light source, that would only be necessary if the days are long periods of time as you suggest. If they were actually roughly 24 hour days, then there's no problem with any plant surviving through 24 hours without sunlight. I can take a plant out of my garden that is healthy, yes, God would have created all healthy plants, and set it in my basement in the utter darkness of a closet and it will live for about a week before it will begin to show any real trauma from lack of sunlight.
I do agree that there are things in the Genesis 1 account that people don't really take the time to think about, but I imagine we're not speaking of the same people who are lacking in their thinking.
God bless you.
In Christ, Ted