If I could speak directly to the op I would recommend flipping back to a "rightside up" model and doing dumb, mirror, 1:1 backups to rsync.net and then configuring a day/week/month schedule of ZFS snapshots on that end.

Those ZFS snapshots are immutable / read-only so they not only serve as retention, they protect against Mallory (and ransomware and malware, etc.)