I now know how @backblaze makes their money...

Online restore only supports zip files so it's limited to minor
restores. To restore more than 250gb I have to pay them about $199
to fedex a drive to me in about 3 days. In the end, it may be well
worth it. It took almost two weeks to back up that much data over
the Internet. Probably the same if they had a real restore service.
I'll let you know when it arrives and how it goes.