Users LOVE our app but growth is flat. What would distribution in app stores look like?

Polar is a Personal Knowledge Repository for Windows, Mac, and Linux.

We launched about 1.5 months ago and were covered on Hacker News.

Our user base LOVES our product and I think that we've hit product market fit with our small community.

We have about 2000 weekly users and 350 DAUs.

The problem is that our user base growth is flat.

If we're covered on something like Hacker News we get new users from them and about 30% stay and keep using the app with no churn, but we're not attracting any new users.

I think the biggest challenge I have right now is customer acquisition:

1. I can't prove that we have product market fit in a larger market because we're not growing.

2. Doesn't make sense to focus TOO much on revenue as it wouldn't yield much cash anyway. It would validate that we have customers that are willing to pay though!

3. I'm obviously not getting much feedback from new users.

Here's what I'm thinking of in terms of user growth. I'm mostly thinking out loud here as I wanted feedback.

1. Implement cloud sharing and cloud sync. This is going to be our revenue stream. It's going to be freemium and priced at 7.99 USD per month. This would prove that customers are willing to pay BUT the challenge here is that it's technically difficult to implement and I've already spent three weeks working on it.

2. Focus on improving SEO. This is not a viable short term solution. It's going to take a LONG time for our SEO to build it up and it might just make more sense to focus on other growth avenues and let SEO build naturally.

3. Focus on distribution in the Firefox and Chrome extension app stores and also work on getting into the Mac App and Windows App stores. I think this might be a viable solution as users are really intent driven here. Some people are reporting 200-500 downloads per day of their extension. I'm not sure this is viable but I think I want to do a basic test if I can bang out an extension quickly.

4. I was also thinking of implementing some social sharing functionality to share with Twitter but I'm not sure our users would actually use this functionality.