[tor-relays] Number of connections on dir port

[Logforme]

After reading this post 
https://lists.torproject.org/pipermail/tor-relays/2018-May/015277.html I 
started looking into what is happening on the dir port on my relay 
(855BC2DABE24C861CD887DB9B2E950424B49FC34)

The bandwidth ratio of dir/or traffic is around 3% to 4%. Not excessive 
according to the linked post.

Looking at the conntrack table I see many IP addresses (usually from 
Ukraine or Russia) with 100+ connections. Atm there are around 10 IP 
addresses with 100+ connections and around 30 with 10+ connections. None 
of the IP addresses I've looked at are Tor relays.

Some questions:
Is this expected behaviour against on a fallbackdir flagged relay?
Does the DoS prevention implemented recently address abuse against the 
dir port?
I read that newer Tor clients don't use the dir port. Correct?
Do Tor relays use the dir port?
Can I remove the dir port from my relay without reducing my relays 
usability to the network?

Thank you for any answers.