Love Bullet is the example of a massive fanbase push for saving a manga. I'm uncertain how much it matters because it's a very western push, but volume 1 was sold out and had to be reprinted multiple times because people kept buying it. If it's doing poorly, I'd be very surprised.
You can really tell exactly when the author was told the series was going to be canceled, yeah. It's a pity, because the series was really enjoyable before that moment.