Just be careful as the bubbling in your airlock could just be off gassing throwing you off and you'll end up with a super super sweet Boosie and you'll end up with a super super sweet boozy mess
Lol. Stupid text to speech^
Are you wanting to bottle it still? Or carbonate?
At this point, how much of a difference is 16 and 18% or whatever the difference is?
Rack to secondary while there's still a bit of active fermentation going and age it. If you wait until the yeast dies, you'll oxidize it. Or, I forget, maybe you racked already.
If you want to keep pushing the limits, you could pitch some super high gravity yeast.
Been a year now. How'd this turn out? Guessing you had to age it quite a bit.