As for keeping the batch: depending on what is infecting the batch, it could end up giving it a very desirable 'sour beer' flavor, or it could end up nasty. If you're not dying to get that carboy/better bottle filled with another brew, letting it ride with that infection for a while and then bottling/kegging is a great experiment and you may end up with the best beer you'll ever make. If you don't keg, bottling now is riskier because the infection could continue to ferment your brew and cause bottle bombs, but if you keep a close eye on things and have the capacity to refrigerate a whole bottled batch once they're properly carbed, you might avoid most of the flavor impact of the infection and still be able to enjoy your beer.
If you do choose to let it ride, wait longer than 2-3 days between final gravity readings before bottling: many bacteria ferment much more slowly than brewing yeast, so 2-3 days may not be enough time to see any difference in a beer that's still actively fermenting. Also in addition to racking and bottling from under the pellicle (infection), I would recommend tossing the pellicle in a sanitized jar and keeping it in your fridge. If the beer turns out awesome, you'll have the bugs saved for a future brew.