I am getting tons of packet loss while playing Fortnite, lags out many times per round.

You are not alone my friend there are hundreds of us on here with this problem. No solution yet and it has been over six months. There is a reddit post on fortnite and an epic team member acknowledged they are aware of the situation and how the servers are handling udp packets from Cox and its issue it has on the clients upload side. That was some time ago and havent heard anything since. I will look for that post and paste it here.