Upload & Sell: On
You have the wrong priorities. The Grain, B&W or JPEG artifacts are not important at all.
"The Decisive Moment" - this is the most important thing.
I agree 100%. The decisive moment is the most important thing.
Grain, B&W, JPEG artifacts are also important and within your control. Not as important as the moment itself, but important. Presentation and the context in which they are presented affects your clients' perception- I am sure you know this. I'm admittedly not the best at this, but I at least know what NOT to do. These are minor concerns-- spit and polish on an already great product. Its like that new Cadillac in the showroom that just needs a wash and wax; it's still a Cadillac.
It's a simple fix for you really, dial back the resize sharpening, up the quality, and re-export from lightroom, black point issues aside. It happens to me occasionally, and it takes 2 minutes to redo it. I use Morgify to add my watermark automagically to each photo so I don't even have to do that step in PS.