The missile has a lot of major issues, but that's not what you are asking for, so I am just going to focus on the "hitting" part.

- the missile doesn't have any roll thrusters, change the settings of some of the thrusters so that your missile can actually control its roll

- the missile doesn't have any "up" thrusters or wings, so it constantly has to pitch and push itself up with the main thrusters, adding some would massively boost the stability and controlability of the missile

- you need to add AI PIDs to your missile, I advise Yaw, Roll and Pitch at least. Tweak them until the missile is stable (keep the integral value at maximum, keep the derivative time low, and lower the first slider until the missile is stable)

- remove thruster balancing from the AI routines, it sucks, never use it ever.

- 6-axis maneuver AI sucks, use Hover instead (Hover will only works if you give it some "Up" thrusters

- change the behaviour (battle) AI from Ram to Bombing Run and tweak it until it hits