Sorry ... didn't mean to 'hit below the belt', but ... it's always been upwards. :|
I too had an issue with migrating a Windows to Linux site that had large DB (not as large as yours but large enough) ... It was not only a move of platform but a move of DB ... MySQL to MariaDB. MariaDB hadn't been tweaked yet. Grumble, grumble.
Thank goodness I had a dedicated DB box. Did go the route of using nano for search and replace on an sql before importing ... no issues ... but it sure took a long time .... 30 minutes if I re-call correctly. In the meantime, site in maintenance mode. Don't think that can be helped.
Even had to remove rows in the large logs tables .... all those past a certain epoch time stamp.
I'd gladly give up some very old logs for moving forward.
'spirit of sharing', Ken