Reno - one thing I'm not following: in your initial post you mentioned there is no database copy, but in the latest there's a mention of a database copy. Are we talking about the same database, or have you added a mailbox database copy since the original
post in order to work around the crawling issue against the original DB ?
Once a database copy is suspended, its copy queue length will start growing, since essentially you're telling Exchange not to replay any log files against that specific copy. Also, the log files won't be removed from the other DB copies as well ("In
Exchange 2013 log truncation doesn't occur on an active mailbox database copy when one or more passive copies are suspended" in Database Copies and Log Truncation in
this article).
Did you try seeding without the catalog data ? "To seed just the mailbox database copy without seeding the content index catalog, use the DatabaseOnly parameter when running the Update-MailboxDatabaseCopy cmdlet" in the same aforementioned article,
section "Seeding a database copy".