first off, you do NOT want to lower your snr margin, you want it to go up, not down! i would recommend setting dmt back to default.
getting past that, unless you notice a major jump in line stats (margin going UP) by plugging it into the nid, you aren't going to be able to get anything faster than what you have now.
some info to help you out:
[dsl line stats guide - DFA version]
<6db: not good
6-12dB: marginal, should get line checked, but if it works, it works
>70dB: no dsl
69-60dB: lowest tier dsl
59-50dB: good for up to 5Mbps
49-40dB: good for up to 7Mbps
39-30dB: good for up to 10Mbps
29-20dB: good for up to 15Mbps
<20dB: you can get whatever you want, usually
>19dBm: maxed out, not usually a good thing