You didn't state the OG but my guess is that your beer is done fermenting and so the gravity won't change. Yes, 35 is okay for a lagering temperature. 17 days is no problem. Many lager brewers do a "diacetyl rest" at 60 degrees or higher (I just use room temperature) for anywhere from a few days to a few weeks near the end of primary fermentation. Although your primary fermentation is over, I would still recommend it unless you are in a rush. Take your beer to room temperature for a week, rack it to a secondary, put it in your fridge at 35, and forget about it for a few months.