OG Debockle

I have a problems with my Munich-style Bock I brewed today. The whole session went smoothly (seemingly). I even did my first decoction mash without any serious problems. Mashed in at 129, pulled about 1.5gal and heated to 150, let it set at 150 for 15 minutes and then brought to a boil. I put it in my tun and the temp was low so I pulled a gallon and reheated to 175 and returned it to the tun. The temp was 149 so I let it sit for 45 minutes and sparged. I got about 2.5 gal, so I heated more water to 173 and right in the tun. I got about 6.25 gals of wort. I checked my OG and it is 1.033. It should be 1.067. I did some backtracking and my thermometer is erratic and up to 20 degrees off (brand new digital thermometer that seemed okay when I checked this morning). I have not pitched the yeast yet. The carboy is in my fridge cooling to 50 before I pitch. Can I boil some DME and add to it to bring up the gravity? Should I just split the carboy into two and make some wort from 2-row to add to both? That would dilute the Munich base, but how would that affect the bock? Or do I just pitch and write this off as lesson learned about a backup thermometer. The recipe is below.

11# Munich Malt
1# Pilsner (2 Row) Ger
.5# Caramel/Crystal Malt -120L
.25# American Chocolate
1 oz Tradition 60m
0.5 oz Hallertauer 30m
1.0 oz Saaz 15m

Safale S-23 yeast

Thanks

So, did you measure you wort after the boil or after cooling?

I measured the OG when it was around 65 after the boil. Even with the hydrometer correction, I should be 1.064 or 1.065. This is the first time I have ever been more than .008 off.

Were you boiling wort or grain? Not clear from your description. Decoctions involve heating part of the grain. If you boiled wort, you destroyed the enzymes.

Okay, that makes sense. My instructions said to boil, I should have thought more. I bought 3# of DME(Light) and added it to my wort while reheating. I let it cool down to 50 and pitched my yeast. It is slowly bubbling and it has only been 20 hours. I took another gravity and I am now at 1.058. Not perfect, but much better. The wort has a good taste. Deep malt with a caramelized note to it. Hopefully, I saved the batch. I ended up with only 4.5 gallons, but if I can save that, the 1/2 gallon is a good price for education.