Why coin wallet shows only 1 connection?
As you said you have only 1 IP hardcoded in chainparams.cpp and when you run your wallet without any .conf file with added nodes it will lookup only for the IP given in the source code.

If you want to add more nodes just write:

addnode=ip.ip.ip.ip


in your coin.conf file. Restart your wallet and it will try to sync to new nodes also.

If you need to hardcode the IPs in your wallet you can contact me here: https://bitcointalk.org/index.php?topic=3196213.0