1.092 to 1.025 = 78% App. Attenuation
Wyeast gives the attenuation range of 1388 as 73-78%
1.016 will get you to the upper end of the FG (and ABV) of the BJCP guideline, which is about 83% attenuation....
I get a different result. I get almost 73% apparent attenuation, not 78%.
Apparent Attenuation in % = 100 * (OG – FG)/(OG – 1.0).
Apparent Attenuation (%) = 100 * (1.092 - 1.025)/(1.092 - 1.0).
Apparent Attenuation (%) = 100 * 67/92 = 72.8%
I would give it another week or two in the fermentor (re-rouse, if you wish) to finish up and then bottle and/or chill to clear then keg.
You may want to split batch if you're entertaining the idea of adding Brett, i.e., don't add it to the whole batch.