How to maintain sales after a successful launch?

I launched www.techpresslist.com on the 25th August.
(a short intro: the website gives startups 100 journalist contact details for pitching their story to for $20)

I was surprised by how well the launch went! I got 17 sales in the first two days, made the Product Hunt Top 10 and made profits from day one. So far, so good!

However, I'm having trouble now post-launch and sales have dipped. I suppose in all honesty I didn't do enough preparation for sales growth.

Some initial ideas to keep sales going:

1. Contact startups directly and cold-call/email the product. This may not be ideal as I have to make lots of emails to make a sale. On the other hand, one sale = pure profit as I've covered my costs, aside from my time.

2. Increase the number of countries covered to increase appeal

3. Increase the number of contacts covered to increase appeal

4. Make a deal with sales people working on commission. A trade off between having less money but doing less of the cold-calling etc

5. Build up Twitter followers and/or blog more so the website gets out there.

6. Add a subscription box so I can contact potential buyers who aren't ready to buy but like the idea.

Any thoughts or suggestions would be appreciated.