He is being childish, but if I am completely honest, it sounds like you are a little too. Not in how bothered you are by the situation (understandable), but more how you perceive it.
I totally understand wanting to just do the work and cut the meaningless chatter, but the reality is a job usually has more abstract requirements outside of specific job tasks. One of these is getting your manager to like you. Social cohesion is one of the things workplaces tend to look for.
Not every manager cares about small talk perhaps as much as yours does, but that’s the situation you are in.
My advice would be to decide on one of the following 1) work elsewhere where you can thrive without this obstacle, 2) develop the skill of faking being interested, or 3) do nothing but get frustrated and possibly miss out on promotions or similar.
Wishing you the best, from a socially inept person with autism who relates to that dread, haha.
Having additional virtual network interfaces on VMs is completely normal, ens18 does indeed sound like the right one you should be looking at.
Seconding the other commenter who mentioned the possibility of a second DHCP server.
Is your Proxmox host wired via ethernet to the pfsense? Or are there WiFi APs in the mix anywhere