hey Jam, Im not sure if your tplink device is really hacked, can you tell me your current network topology ? maybe I can help you, what's more, I think for this kind of security issue, you had better...

hey dude, how did you tes t the speed?Using speedtest or something like this? I think speedtest is not accurate at all, I suggset you test this using professional tools

hey dude, I think you can set up two connections and each one have 10 users at most

hey dude, I have a R480T and a ER5120, I think if your bandwidth is not very high , so both of them can meet your needs of bandwidth, but ER5120 has some features which 480T does not have ,such as...

hey dude ,can you draw a picture of your topology? And what is the ISP box? Is it a modem or somthing like this?

I think you can try to use the access control and the app control to do the settings