When this "steeps", it's mashing (or at least trying to). I'd give it a bit more Munich, or some two-row to get more enzyme activity to work over the oats, and I'd raise the temperature to 158 (perhaps even 160?) for thicker mouthfeel. A less-fermentable malt extract would also be good, but those are harder to come by now, so fix it in the mini-mash portion.
As for dark flavor (and color, if you want color), I'm a huge fan of chocolate malt, to the point that other people don't agree with me - but a pound or two or three or four is not out of place if you want a serious dark beer, IMHO. That should also help some with the mouthfeel.
If you don't do full boils on extract batches, it's very easy to get whacky OG simply from poor mixing of concentrated wort and water.
Re-filling the pipeline - got a lot of brewing to do.