Unfortunately the OIDs in the SNMP MIB were not readily documented anywhere, officially or otherwise.

I did a bit of hunting and came up with the following information.  Maybe someone else will find it useful.

Upstream Line Attenuation (Gauge32)
.1.3.6.1.2.1.10.94.1.1.2.1.5.2
Downstream Line Attenuation (Gauge32)
.1.3.6.1.2.1.10.94.1.1.3.1.5.2

Upstream Speed (Gauge32)
.1.3.6.1.2.1.10.94.1.1.2.1.8.2
Downstream Speed (Gauge32)
.1.3.6.1.2.1.10.94.1.1.3.1.8.2

Upstream SNR Margin (Integer)
.1.3.6.1.2.1.10.94.1.1.2.1.4.2
Downstream SNR Margin (Integer)
.1.3.6.1.2.1.10.94.1.1.3.1.4.2