Basically, I am you :-)
There is definitely hope but it might need some cash and help. And it might just be a shocking line, poor quality MPF or interference outside the house. Tiny things in the house make a vast amount of difference with attn so high and signals so weak.
I have a ridiculously long line, 63.5 dB ds attn supposedly, four miles from the exchange Broadford Isle of Skye, and get 1.75 Mbps per line.
I suggest.
(0) read all my posts, esp the early ones, and a couple of v recent ones.All known tips there.
(1) Mains filtering.
(2) Try Netgear DG834v3 (not no G, ie non-wireless) from ebay £10. Must be v3. A savage performer, needs latest f/w., might be specific to TI exchanges. Also DLink DSL-320B from aa.net.uk shop only! so it comes preconfigured as a modem, not a really bad router. Dirt cheap. These I am using right now, but am considering going back to give the Netgear modems another try for comparison to refresh my memory.
(3) at least talk to Andrews & Arnold aa.net.uk. Talk to tech support and sales. If your line is broken, they will sort it or your money back. A&A will beat BT Openreach up for you if needed.
(4) shorten all internal phone cables and dsl cables to nothing and get rid of all phones and extensions.
(5) if need be, book BT Openreach to do a “change point of entry” if this will help you shorten links and get your modem right close the the NTE5 and make it be where you want to work. Forget wireless, don't let the wireless coverage placement wag the shortness dog. Get a separate high quality wireless access point and place that where it suits you best,meith a long length of Ethernet cable to it if needed.
I use A&A with three lines bonded together, and combined upstream as well as downstream. My line is just as long as yours, and I get a combined 5.2-5.5 Mbps ds throughput.
When youve read everything Ive ever written :-) do come back and ask anything. But I would let A&A do all the work, that's what they get paid to do.