Weeks to do 600GB over tor, tunneled through a VPN sounds about right.
Discussion
Really!
Interesting, most synching is done using Tor, so is it the VPN that causes the issue?
Also, bandwidth has little to do with sync speed in my experience.
I've synched an RPi 4 over a 1GB fibre connection in a week and I've also synched a high end Lenovo NUC on a 15Mb/s FTTC connection in just over a day.
Yeah CPU and disk are bigger factors than network