How much do we owe you for the participation trophy, and your blue hair dye? Such a magnanimous gesture.

Teehee!
I kid, I kid we all try to be supportive here, but I believe this man is looking for competition, not kudos.
You know, I have no clue, but I know it is a lot lower than it used to be. I use half caff for my big yeti in the morning, then I have another 2 sometimes 3 single serving cups of coffee a day from the machine at work. On weekends I will have 2 of the big yeti's full of half caff. Then when it comes to preworkout it is normally 2/3-1 heaping scoop of Pump Addict so anywhere from what 160-300mg in that.
Are you chasing a high, or looking for the performance improvement? it is like
@Hyde said, pretty static once the initial few days are over. So to keep feeling the buzz of it you may have to continue to boost it up here and there, but to get the desired effects, is different than feeling the buzz. That being said, you are no where near any limit I have ever heard suggested, so you have some room to go before hitting even a moderate cap there.
As I think Dustin mentioned, do what works for you with it. If using too late is a nono avoid it, if sleep gets worse avoid or lower it. Also if at some point you know you need an extra kick have that extra kick. If afterwards it has a bad result (your sleep or stress levels) then don't do that.
I have seen A LOT of rowing in this log over the years, and I would be surprised if your rear delts are truly a weak point. I would almost be willing to bet that your posture is the issue there. Anyone who thinks rows are not hitting the rear delts sufficiently to stimulate growth are simply mistaken. My guess is like 80% of us you have upper cross syndrome, IE tight chest / shoulders rolled forward. Well you can't really display the rear delts when they are pulled forward and stretched flat. They look unimpressive that way in the same way that trying to show of your quads while sitting on your heels. It ain't gonna be impressive. I go from looking like my rear delt is literally missing to looking like it is sticking out off of the top of my back just by depressing the scap, externally rotating and retracting the shoulder slightly. Then BOOM it drops out of hiding and looks a bit silly.
That being said big rear delts really do make the whole shoulder pop and extra/isolated volume will bring them up. Just saying with limited time, maybe work on the posture I think it would make the biggest difference in the appearance of your delts.
Man this Dude ruined Reacher for me with his political BS. I don't care too much what side of politics people are on in general, but when they say horrible things, call for blood in the streets and say if you don't like it then don't watch my shows. Well damn man. You got it. It just sucks because I have liked his stuff for years, but he drew a line and now I am like Ahhh f#ck this guy... whenever I see his face.
Do you feel you misgrooved it, or that it was just too much? If misgrooved, maybe try again, see if you adapted, it not drop back. If it was just too much too soon then you are likely making the right move.