I grew up in NYC in the 1970s. When I heard of Trump's comment, I burst out laughing, mostly because I hadn't heard the phrase "schlonged" in about 35 years. We used it as teenagers to indicate a defeat or someone having been "screwed over". A decade or two ago, a similar sentiment might have been expressed by saying "we're so boned", meaning "we are in serious trouble".
So I would say that the "schlonged" phrase is not directly sexual, not is it gender-specific.