I noticed that you did not mention any form of aeration prior to pitching or after pitching your yeast. I highly doubt that your mash pH was that screwed up that it lead to such a poor fermentation. Sometimes a lack of oxygen (especially with harvested yeast from a prior batch) introduced to the wort can lead to a stuck/stalled fermentation.
Did you aerate this batch well?
Good thought. I aerated this batch as normal although I don't do anything fancy like pure O2. Just a three foot drop when transferring into the fermenter from the spigot on my bottling bucket. Never had a problem before.
I took a reading this morning and it doesn't appear to have changed. I was going to keg but since I can't leave anything alone I added about 6 oz dark brown sugar dissolved in one cup of water. This should hopefully promote a bit more activity, possibly drop the FG a point or two, and get the beer closer to 4.5% ABV.
Tasting the sample now. Kind of has a tangy sourness to it along with some tannic character like you would get from iced tea. Smells fine; malt, biscuit, touch of chocolate. Hopefully it is just from a lot of suspended yeast as this is a very low flocculator. At this point, it is what it is so I am not too worried though it would be a shame to have to dump it...we'll see...