debian-tor             soft    nofile          64000
debian-tor             hard    nofile          64000

- There are a lot of possible syctl tweaks. You could check out https://raw.githubusercontent.com/torservers/server-config-templates/master/sysctl.conf. I use these values on my non-exit relays:

net.core.wmem_max = 12582912
net.core.rmem_max = 12582912
net.ipv4.tcp_rmem = 10240 87380 12582912
net.ipv4.tcp_wmem = 10240 87380 12582912
net.ipv4.conf.default.send_redirects = 1
net.ipv4.conf.all.rp_filter = 0
net.ipv4.conf.all.send_redirects = 0
kernel.sysrq = 0
net.ipv4.icmp_echo_ignore_broadcasts = 1
net.ipv4.conf.all.accept_redirects = 0
net.ipv4.icmp_ignore_bogus_error_responses = 1
net.ipv4.tcp_no_metrics_save = 1
net.ipv4.tcp_moderate_rcvbuf = 1
net.ipv4.tcp_tw_recycle = 1
net.ipv4.tcp_fin_timeout = 4
net.ipv4.tcp_keepalive_time = 60
net.ipv4.tcp_keepalive_intvl = 10
net.ipv4.tcp_keepalive_probes = 3
net.ipv4.ip_local_port_range = 1025 65530
net.core.somaxconn = 20480
net.ipv4.tcp_timestamps = 0
fs.file-max = 64000

- You should install ntp make sure your clock is synced.

- You should install a local DNS resolver (unbound, named, dnsmasq, something along those lines).
 
This guide has a lot of helpful info: https://www.torservers.net/wiki/setup/server