What did your recipe predict would be the Final Specific Gravity and ABV of this batch? Assuming it was indeed significantly higher than where you think it is now, how did you determine the current ABV was 3%?
Bottom line, if the recipe expected a significantly lower FG/higher ABV, adding more fermentables would be the nuclear option (ie: attempting to "dry out" a brew by adding virtually 100% fermentable sugars). Better would be to have yeast finish the job that was apparently interrupted to begin with.
I'd get the beer up to a yeast friendly temperature and add a lot of yeast, and see what happens. Worst-case, you crash-cool the batch for a week to drop everything back out, chill and carb, and have something you can pour over ice...
Cheers!