Since you've gone over the rules, I've gone ahead and added "I_am_Breadbear" to the whitelist. You should be able to connect via mc.indiesquish.com in the multiplayer menu now.
Just a heads up though. The multiplayer server is currently on 1.10 while we wait for some important plugin updates to 1.13 So that's the version you'll need to use to play for now. Sorry for the inconvenience, as we have no direct control over the plugin devs.