What are the yeasts your used? 9.7% ABV may be pushing your yeasts beyond what they want to do. K1-V1116 is a champagne yeast that can eat maltotriose so that might work for you; it is a killer strain so you won't be able to try any other beer yeasts afterwards.
I don't tend to do multi-rest mashes so take this with a grain of salt, but your two mash temps seem low so they may have left a lot of dextrins. Assuming you got a lot of dextrins, you could add some glucoamylase, Belle Saison yeast or other diastatic yeast. I would expect them to work slowly. One way to verify that your fermentation is done, i.e., lots of dextrins, is to do a fast ferment test. I've never done one b/c I'd rather make an educated guess (fun) than be scientific (boring).