None of those changes disabled ipv6? Also, ipv6 is not supported at all in the base, you would need to load the extension..
Syncookies is a protection for certain kind of DDOS. Off by default, should cause no problems when on.
Window scaling can improve your connection, is on by default, and should not be turned off.
ECN is an advanced router feature, easing congestion, but it can lead to dropped packets if old routers are between you and the server. It is off by default.