Stopping fermentation when FG is reached.

It should be 1018?
Unfortunately the yeast get to decide when they are done. As a brewer you are a glorified janitor. Sure, you can cold crash and put them to sleep, but that is not the best idea. Let the yeast do their job.

If you have not hit your targets it means your calculations or process needs some revisiting.
Even still, .001 gravity points is just above a rounding error. Since you are brewing with honey expect the fermentation to be unexpected. Tons of different sugars present in honey, the yeast will take time to get through it all.

Let it be.
Cheers

 

If you were really worried that it would ferment out, lose its sweetness, and not be the beer you want, you could add sorbate and metabisulfite like mead makers and vintners do if they want a sweet beer, back sweetening afterwards as necessary. But I wouldn't bother unless you are 100% sure that this beer needs to be at 1018 to be enjoyable (seems like a stretch to me). And, yes, after doing this, kegging would be the way to carbonate this beer as your yeast would not be viable.

 

If you crash it before the yeast has cleaned up the diacetyl and acetyaldehyde you will end up with green apple butter beer. Best to let the yeast finish and clean up the beer before you crash it.