Whether you use 7777 or 5443 or 12345 as the listening port doesn't matter---it's your choice, but you must make sure the socket in config.js matches. It looks like you left out the slashes in config.js. So if your listen port is 7777 like me, your config.js should have
socket: 'wss://yourdomain.com:7777',
If you want to use 5443 then put that in your bind listen in HAProxy, and also in your config.js.
Port 5555 is the port that the actual Kazoo app uses, so your server line in HAProxy must have port 5555.
The socket line in config.js tells your users' browser where it should connect to for websocket events---this is the protocol and port that you are exposing to the outside, the TLS proxied websocket port (5443 or 7777 or whatever you pick---any port as long as it isn't already in use).
The listen section in HAProxy is what config.js is referring to, it's what HAProxy is listening on from the outside (with TLS).
The backend section tells HAProxy which server[s] to send those requests to that it gets on the public (TLS proxied) side. This will always be to port 5555 on your Kazoo apps, since that is where the Blackhole Kazoo app is listening, and there is no option (nor need) to change that port.