1) The Yaw angle rate is too low for a mobile (ship based) SAM system in this series. Try upping it to 90 degrees/sec. This may not be 100% accurate, but it's a necessary compromise if you want realistic SAM defenses.
2) You may be expecting to engage targets out to 120 km, but not with a radar that's limited to an engagement range of 20 km (as is in the case with your settings). In real life, the first model Sea Dart's max effective range is probably closer to 35 nm, only the newer variants meet the 120-150 km range criteria.
3) You have no noise and counter-measure rejection values listed. In short, "You Jam, no SAM".
4) That ship's data.ini needs to be updated to SF2 standards, as it's lacking radar frequency values, a radar family name, etc.
5) The booster values are way too high, as are the sustainer values. These effect it's engagement envelope, and grossly limit the missile's maneuverability. Try cutting the booster values down to 10 Gs, and the sustainer values to 0.5 (it's a ramjet, after all), and work up from there.
6) Research, research, research! Do your research, otherwise, you'll wind up with what we refer to as another "CCNO"