Launched my screenshot API last week — a traffic spike, then silence. What would you focus on first?

Solo dev here. Last week I launched Shotium (https://shotium.com) — a screenshot & OG image API. "GET a URL, get back a rendered image", plus signed image URLs you can embed in HTML that re-render whenever the underlying data changes. 100 free renders on sign-up, then $15/mo for 2,000.

What I've tried so far:

Product Hunt: launched on a Tuesday. Some upvotes, a burst of visits on launch day, a couple of free signups, zero paid conversions. Traffic back to baseline within 48 hours.
Reddit: my launch posts got eaten by spam filters — new account + new domain, my own fault. A link-free "asking for advice" post finally stuck this weekend.
X: posting while building, but with no audience it's mostly shouting into the void.
So: the product works, uptime is solid, docs are decent (I think) — and nobody knows it exists. Classic.

Options I'm weighing:

Free tool pages / SEO — a free online screenshot tool that ranks over months and funnels into the API
Ecosystem integrations — n8n/Zapier nodes, Next.js/Nuxt OG-image packages, so people find me inside the tools they already use
Technical content — write-ups on the hard parts (SSRF-hardening a URL-fetching service is a rabbit hole), hoping for organic dev traffic
More launch platforms — keep the HN/directory circuit going
If you've taken a dev-tool or API SaaS from zero to the first ~10 paying customers: which of these actually moved the needle, and which was a month of wasted effort? Is there an obvious option 5 I'm not seeing?