Lots of minor problems, what the heck

I brewed an Irish Red over a week ago. Here's the recipe:

9# Maris Otter
.5# Crystal 80
.5# Crystal 40
.25# flaked barley
2oz eng chocolate malt
2oz eng roasted barley

I'm pretty consistently getting 75% efficiency, so this was intended to be 5.25gal at 1.053. After runoff, I collected 6.5gal at 1.046 (all gravities are temp corrected), meaning I was actually above expectations for efficiency. After boiling, and straining into the fermenter, I had 5gal. I usually aim to undershoot my final volume so I can use some top-off water to sparge the trub. So I took my gravity just to see how much water I'd be able to add, and the reading was 1.051.

So there's problem #1... not a huge one but I was really confused - that's never happened to me before (I swear baby!). I know I thoroughly stirred before taking a gravity reading. But it wasn't that far off so I just figured I'd go with the 5gal at slightly lower gravity.

My second problem is with attenuation. I pitched with 1968 London ESB. It fermented at about 68* as expected for a few days, and then seemed to finish up on the fourth day or so. I checked the gravity on day 7 and I get 1.021 (59% attenuation). Crap. So I added some yeast energizer, stirred the yeast up with my racking cane, and lidded it back up. Nothing.

I've come to realize that I think my thermometer was miscalibrated by minus 2*. I intended to mash at 154, overshot to 155, but due to miscalibration this could mean I actually rested at 157-158. An iodine test at 60 mins easily indicated conversion.

Do you think mashing that high could lead to such a low attenuation? I usually get 69% attenuation with 1968. I can understand if it were around 63-65%, but 58% seems a stretch.

Here's another thought - maybe my postboil gravity reading, despite my efforts, really was off. Let's say the preboil gravity reading was correct, which means that boiling down to 5 gallons would mean I'd be around 1.060. This means my final gravity of 1.021 yields 65% attenuation. Is this more feasible than the above scenario?

In any case, the beer tastes great and I'm going to let it sit a few more days and bottle. Probably a rush, but I need more beer for Christmas and New Year's. Damn alcoholic family.

Well, it's a physical impossibility for both your preboil gravity and your OG to be correct if you really went from 6.5 gallons to 5 gallons. The only thing that should be gone is 1.5 gallons of evaporated water. Given that you didn't boil off sugar with your water, one of your gravity readings was clearly wrong. Normally, I would guess that it was your preboil gravity because that's the one that is easiest to mess up by not having the first and later runnings be well mixed. However, given your apparent attenuation problem, it easily could be you OG that's off and you really did have fine attenuation.

I guess I'll go with a bad OG measure simply because it's parsimonious and explains two effects: bad OG reading explains both mismatched gravity readings & poor attenuation. Any other explanation has to have two factors to explain two effects: bad preboil measure explains mismatched gravity readings & high mash temp explains poor attenuation.