I have a similar machine I’ve been testing. Put gen=1 and genproclimit=3 in .zcash/zcash.conf to run 3 of your 4 cores when you run zcash -daemon. The 8 hyperthreads are not real. Leave 1 core free to do regular work at the same time. It’s my slowest machine, but it’s the desktop I use everyday. Get someone else’s .zcash/testnet3 folder from here Z8 .conf file changes and connection issues? - #14 by waterhole
Delete yours ( rm -rf .zcash/testnet3 ) then copy over theirs and be sure to delete their wallet.dat if it is included to keep from messing things up. Do not run as root or use sudo, or you’ll have to start over. Your connections line from the getinfo results above should then say 1 and current block is about 7200 when you are on the main testnet. You’ll get about 5 blocks per day the way things are right now, between 2 and 8 blocks (90% probability). A higher-end new machine will get nearly 1 per hour.