Are you sure that's your desktops IP? Because it's the same as the IP in the fifth screenshot in OP.
Oh, try turning Connection Sharing in the fourth screenshot to distribute a range of IPs
That's a good idea but still no one can join ALSO I don't know how to disable UPnP on mac even though I searched on google.
It's in Blockland - Options>Network>Disable UPnP (Check it)
YOU try joining from LAN server because it's on the same network as you.
This has nothing to do with other people not being able to join