Your target gravity was 1.090, and you used 10 lbs of DME among other things? 10 lbs of DME gets you damn near to 1.090 by itself, was this larger than a 5-gallon batch? I get ~1.133 for that recipe, assuming 75% efficiency. But remember, DME and sugar are 100% efficient.
It still shouldn’t be up at 1.200 though, I don’t care what your efficiency was. It probably is a mixing problem.
You can add boiled cooled water or a weak batch to dilute it. It’s up to you, either of the methods will work.