Goto gateway's page »
192.168.1.254/ by default. Find and post screen shot of broadband/stats showing noise margin, attenuation, error table, sync rates... and possibly diag/dsl page showing few more stats plus retrain history with a reason column.
Don't reveal publicIP & MAC. Can also use UVRealtime: esp. for its estimate of your twisted pair length based on attenuation.
Do you have uverse TV? Speed tests (i.e. speedtest.net for example, avoid dslreports) should be done from a single Wired client, with all other clients, DVR, TV boxes off, disconnected, or idle. Configure 5031NV's wifi to WPA2 security, and avoid auto channel selection, pick from 1, 6, or 11 or use a stumbler or inSSIDer program to select least congested of these.