Linksys EA6400 - PPPOE issue

        I have the following problem with my router : The ISP provides 500mb/s and my router only outputs on wire or wireless 200-230mb/s.

The set up :

1) Router Linksys EA6400 

     firmware : 1.1.40.160989 

2) Network cable : Gigabit 

3) Wireless adaptor : Linksys WUSB6300 

4) PC : i5 4690 ; 8GB RAM 2400MHz ; SSHD 1 TB; Motherboard Gygabite Z97

5) Connection on router PPPOE ; ISP : RDS Romania.

       ISSUE : I always get no more than 230mb/s on tests (www.speedtest.net; or other tests sites and benckmarks) wired or wireless I have the same speed “limit”. The ISP came and tested my connection and on the router INPUT (internet) I have 500mb/s no fluctuations.

    Also I have drops on wireless after a couple of hours of continuous internet traffic.

What I have tried :

1. Rebooting router
2. Factory reset
3. Firmware downgrade and upgrade again

-Nothing worked 

Does the router have conflicts with the PPPOE connection ?

Might the router be broken ?

Please help me with this issue.