Stopping an active fermentation is like stopping a freight train- not at all easy, and sometimes impossible.
Since your OG was managable, I'd suggest doing it the easy way. Let it ferment out completely. It will then clear, and stop dropping lees. Once that's done, it's easy to stabilize the wine with sorbate and campden and then it can be sweetened to taste.
I like to set up a few samples, and then add some simple syrup to it until it's just right. Then I check the SG. And then I sweeten the whole batch to just under that SG. What I mean is that if I love the wine at 1.010, I'll sweeten it to 1.008, as it seems to get sweeter tasting in the bottle.
I'm not much for sweet wines, so the few wines I sweeten I tend to sweeten to 1.000, or just off-dry. I don't know what you will like best, but if you set up several samples as I do, with some at 1.000, 1.006, 1.010, etc, you'll see which you like the best.
Broken Leg Brewery
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