Are Insta (and FB) devs not embarrassed that HN has become the customer support channel for their products? Does it not come up during standup conversations?
I don't know how it would work with the account currently being hacked, but this is what the verified paid offering that is rolling out should help with. Have you reached out through that channel? Is there one? (Not a user of their products, just keep abreast of the news where it was announced.) Sorry I can't be more helpful, sounds like a really big hassle.
Maybe its a good time to rebuild from a personal home server that would give you more control over it.
Post to HN, which you've done, and hope real hard to get the attention of an Instagram employee.