I would add:
Getting good PR in premiere outlets will give you so much more than just the first 1,000 customers. It can open the door to all kinds of opportunities, from being invited to speak at the conferences your customers attend, better recruiting, being noticed for partnership and business development deals, an being top-of-mind if you start looking for funding.
Embargoes are a tricky logistical detail, if you're using one, you don't want to leave any room for error. So aside from mentioning it in the pitch, also include something like "Embargoed until 4/13/17 at 8am California time" in stand-out font at the top of any fact sheet, press release, etc. that you share with the journalist and be sure to mention it in all your confirmation emails.
Once you get awesome PR, figure out the best way for it to live on your site going forward. I see lots of startup landing pages these days with logos like TechCrunch, Wall Street Journal, etc across the bottom but no links to said articles. I can understand why, for conversion rate optimization, you may not want to include the links on your landing page. But for ultimate credibility and (possibly SEO juice) consider having a separate section on your site for press where the actual links to the articles can be found.