Ok so first: there is no threshold for the Medium Partner Program: https://medium.com/partner-program

Read this blog post for more info: https://blog.medium.com/new-partner-program-incentives-focus-on-high-quality-human-writing-7335f8557f6e

Second: the Boost Nomination Pilot Waitlist is currently open to editors who manage Medium publications that actively accepting submissions from other writers. If you're a Medium writer but not a publication editor, or if your publication only includes your own writing, you're not eligible for this program at this time.