If you still need helps with the prefixes try PExChat permissionsex doesn't support chatmanager anymore so inless you get a permission plugin...
How many players are on? Try the clearlagg plugin there might be a lot o entities around.
The problem might be spare chunks loaded try getting clearlagg and running the unload chunks command if its still laggy I think you'll be stuck...
It all depends on how far they walk how many entities they drop and even how hight they build, it all adds up but you can try clearlagg to get rid...
Im not sure but it loos like your server needs a little bit more ram or make sure your using the mac server jar (vanilla) or the correct starting...
Check your internet speed at www.speedtest.net If your download is around 20 ping is at about 50 or under you should be good.
I think there is also a plugin that links servers or splits them up.
If I'm correct there is a way I think I haven't used the plugin in a while.
I would get the clearlagg plugin and set it to go off every 2 minutes or so you probably have a lot of entities.
I would use multiverse, its a little hard depending on what your doing though.
Try updating your java, or if your running a different operating system other then windows look it up for you os/operating system
If your using 2wire did you select the computer and add the port with TCP and UPD?
How much ram Does it have. How much ram does your computer have, I need more information.
I agree Change the port in the sever.properties or just restart your computer.
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