Hi Luger,
It looks like you’ve figured out how to calculate an angle between two vectors already, so I believe you’re looking for a missing vector instead, as you illustrated being 90 degrees from the target point.
Check out this in-depth article on CrossProduct, and I think you’ll find how to calculate what you need from there.
Per your second question, I think you were asking how to compensate for gravity and the rocket’s weight so that it reaches the target in a linear fashion? If you’re choosing to calculate the minimum force needed to compensate for these elements (probably not practical), I recommend this formula. A quicker option is to utilize the LinearVelocty instance and set the MaxForce property to a prodigious value (like math.huge), and you’ll only have the velocity to care for.