I get the impression that whilst you've been back using the Wireless, the drops were pretty much as before you tried the 200AV system and using this system just made things worse? This tends to suggest that interference may be the cause.
Your line stats look good, so we better check the basics first.
Listen to your phone line, can you hear any crackling or other intermittent noises? Do you recall hearing any in the past?
Do you have extension sockets and are you plugged into one or are you plugged into the master? If you have fixed extensions and wiring, do you know if the bell wire is still connected?
If you have extension wiring, can you plug into the test socket which is behind the removeable lower front part of the master linebox. Be careful not to pull out any extension wiring connected to the removeable faceplate. Check also that all extensions are dead with the faceplate removed.
Also look to see if any wires are connected to terminals 3&4 on the rear of the removeable faceplate.
You'll need to stay connected to the test socket like this for a while to see if this stabilises the situation.
If there is no change, try another filter. If still no change try another modem/router.
