RT-AC88U constant issues with speed

I ready to dump my RT-AC88U. It is killing my internet speeds. I'm getting 1-4Mbps download. I am on Comcast 300MB download plan. I have to constantly reboot everything and change cables. If I can't get help I need to get something else. I purchased this 11/24/16 any options for return? Also what router out now should I get based on this model my needs should seem transparent. Looking for TOP tier routers.

Speed Results
DOWNLOAD SPEED
4.63 Mbps
UPLOAD SPEED...

RT-AC88U constant issues with speed