Hi dabba,
To answer the other questions, yes leave the modem/router on 24/7. You are not close enough to the exchange and your line seems to have been too troublesome to have the luxury of switching on&off when you wish, if you want the optimum speeds from your line. That last sync speed (DSL Connection Rate) 4992 is the best for a while, so you want to hang on to it.
If you can post your modem/router ADSL line stats, this will be more informative about line conditions than speedtest results. Once/if your line is stable your profile will rise (a reminder it can take 3/5 days) then throughput speeds will improve.
I presume you are still connected to the Test socket where all the extension wiring & sockets are dead (which they should be). If at some point you want to return to a more normal setup, you'll need to look at this internal wiring. If so & when you have time could you look at the wires connected to the back of the faceplate you've unplugged at the master socket, hopefully there will be one cable with single wires connected to the terminals.
You should find a Blue+white trace on terminal 2 and a White+blue trace on terminal 5. You may also find an Orange-white and White-orange on terminals 3 & 4. If you unscrew your extension sockets from their boxes you should find identical colour wires connected to them. You should find two cables at the first extension socket (don't know how many you have), and so on until you get to the last one which should have one cable.
On the back of the extensions you hopefully will NOT find a yellow "sausage-shaped" capacitor on any of them.
