It's surprising you have any sort of a connection with a SNR so low.
10 is normally considered the minimum for a reliable connection.
And the upper limit attenuation for 2Mb is 43dB, so you're way outside that too.
If your connection was working before but has suddenly become unreliable, it looks as though something may have happened - water in one of the connections of the line or some other nasty like that. Is your voice line OK? It sounds as though BT should be having a look to see what's gone wrong.
Do you have the figures for your line when it was working reliably? Increasing the speed to 2Mb may make them a bit worse, but not drastically so.