I'm certainly no expert, but additional yeast should not hurt anything, yet it may not help anything either. But you're not really sure there is "anything" that needs fixing at this point, right?
You kind of set yourself up for problems and made it difficult on yourself by tossing in way too little yeast in this heavy brew.
Generally.... the longer you let it ferment, the higher the ABV will get, and the more difficult it will become to get some fresh yeast established.
This will turn into beer for sure, but not likely to hit it's potential flavor and attenuation.