MySQL - Fastest restore of 1TB database
If you have "too many" threads doing the restore, they will stumble over each other and might run slower than if you used a fewer number of threads.

Add on innodb_buffer_pool_instances=16

I assume you are using SSDs?  Otherwise, some of the settings are too high.

If you are I/O-bound, then probably there is nothing you can do to speed it up.  Except...

In the future, consider setting up LVM so that both dump and restore can be on the order of one minute, even for multi-TB dumps.  This is because of the "copy of write" technology at the block level of the OS and disk.