I have about four thoroughly edited unpublished novels right now, and I have accounted for a lot like: story (developmental editing), logic and consistency, flow and style, and now including for shorter sentences. For shorter sentences, I was mostly taught writing from an academic point of view. This being that in academic papers, long sentences and the use of the semi-colon being the norm and how I had to cut down completely when writing my novels. But anyway, I have about seven to eight revisions for one of my novels and about three for my second, two for my third, and two for my fourth. I have edited objectively but I was wondering when is it enough?
You should stop editing when you don't think you're significantly improving the writing any more.
With that said, now may be the time to have an outside reader give you feedback. You might also want to do an edit that isn't for any errors or deep structural issues, but that tightens up the work, and removes anything excess or extraneous, so that the final book is lean (and closer to your word targets).
Also, I'm not necessarily a believer that every writer needs a professional editor, but you might want to think about hiring one when you get close to your final draft.