Mothers Day Imperial Stout Brew Session

Couldn't fit all 22 lb of grain into my 5 gal cooler, so I split it 50-50 with my brew kettle for the mash. Mashed in ~1 qt / lb at about 122 degrees for 20 min, then pulled about half the mash from the cooler for a decoction mash. Brought it up to about 158 degrees, held it ~20 minutes, then boiled it for 15 minutes and added it back in - but it seemed way too hot, so I mixed in some of the mash from the boil pot to cool it and be sure the enzymes weren't denatured. Then it was too cool, so did another decoction. Got the cooler to about 154 degrees, then direct heated the pot and brought it up to about 152 degrees. Let both sit for ~1 hour, then put the contents of the kettle into the cooler and attempted to sparge - but I think because of the rolled oats and rolled barley, the sparge was stuck. Eventually I just went with it, had a very long sparge, and finally got about 6 1/2 gallons. Boiled ~1 1/2 hours (after a boil-over at the point of boiling) and got about 5.5 gal of good wort.