You have listed the output of nmcli d which lists the managed devices. However, you are trying to delete connections which are a different item for nmcli. From the man-page:
NetworkManager stores all network configuration as "connections", which are collections of data (Layer2 details, IP addressing, etc.) that describe how to create or connect to ...
Let me answer my own question. Not sure why it works this way but it works. I simply allowed "password logins" and it all started working perfectly well. It connects using ssh keys anyway without any password prompts but.. nonetheless allowing password logins in ssh solved the issue (I had it turned off earlier). Hope it will help someone too.
2021-06-23 19:44:26.395 UTC  LOG: could not bind IPv4 address "10.100.0.107": Cannot assign requested address
2021-06-23 19:44:26.395 UTC  HINT: Is another postmaster already running on port 5432? If not, wait a few seconds and retry.
2021-06-23 19:44:26.395 UTC  WARNING: could not create listen socket for "10.100.0.107"