The max “upload” (import via phpMyAdmin) is actually 7 MB, but that does not mean you can’t import it
Check out this Dreamhost Wiki article on Migrating MySQL databases for instructions on how to import the larger database via the command line.
Dreamhost support made the backup available for you already, and while I’m sure they would be happy to go ahead an import it for you if they have the time, that is not really part of their function, and you can do that for yourself. I suspect they are dealing with other customers whose problems absolutely require their assistance before getting back to you on the import request. They don’t seem to be particularly “short staffed” or “backed up” right now, as they are only showing half the outstanding support requests now as they were showing last week (though I suspect weekends (hobby users) and Monday mornings (business users) are always a bit hectic for them),