That is way too long, for 9GB, I'd expect the import will be done in a much much short time. Then I am not sure, it could be more possible reasons. Maybe you can find a place that has a faster network as a workaround method.
Please use lsphp81-mysqlnd.
Latest mcrypt build is lsphp74, e.g. lsphp74-pecl-mcrypt
So you might want to build the package by following https://docs.litespeedtech.com/lsws/extapp/php/extensions/
For non-rewrite rules, OLS will just bypass it, so you might want to find out what is causing the 500 error first. Does anything show in the error log?
Please upgrade to the latest version, if a new core file is generated, then follow https://docs.litespeedtech.com/lsws/cp/cpanel/bug-report/ and share it to support@litespeedtech.com