Well, personally I guess I've always thought of "moody" as "dark and undersaturated". This is the former, but certainly not the latter. But hey, I have no idea what I'm talking about.
It's actually very difficult to have a room that's too bright. But if you're concerned ... I dunno, maybe go for 80s? But don't risk being still too dim.
If you are going to defy all logic and press ahead with this action or action pair, don't forget the noise layer clipped to the blur layer. There's a big risk of banding with such a large blur.
I am completely flabbergasted that you're even considering this. Blurred vignetting is every bit as bad as selective coloring. No self-respecting photographer should be considering it.
The notion that an award-winning baby photographer would even use this method once is astonishing. The notion that you would be considering using it so much that you need an action for it is sickening.
Sorry, I've never found a way. You would have to make it as two separate actions ... eg F3 duplicates the layer then chooses the Marquee Tool for you. Then you do your selection. Then you hit F4 to run the second action to do the feathering and blurring.
Again, this statement points to the bigger problem. You definitely need a brighter room for your editing. So maybe you need to see if there are 100W bulbs available for your fittings?