People engage things: a) when they're brand new, or b) when they're nearing a deadline. We lose interest in that middle space.

You should clearly and visibly limit your campaign to between 30-45 days. With this duration, you have a 1 week initial push, a buffer period for people to share and remain engaged, and a "final push" week where you go all out. Kickstarter is a sprint, not a marathon. With all the preparation you did in the last milestone, you should be able to focus your efforts into a high quality campaign.