There are SO many places I could go with this. Would you happen to have a video clip of you doing the kicks, along with an explanation of when you experience pain?
Also, where in the hip is the pain happening? Hip socket? Outer hip (e.g. piriformis-ish area)? You mention the greater trochanter hitting the pelvic wall. I am having a hard time visualizing this.
When you talk about your "150-degree" side kick, from what body plane are you measuring your angle? Is this a measure of your leg's external rotation, or of the angle of your leg to your body? In ballet when we talk about a "90-degree extension" for example, we are referring to the leg being held at about waist height to the front, side, or back. So are you talking about 150 degrees in terms of leg height, or leg rotation? I am just trying to understand what it is you're describing before I reply.
Increasing your "turnout" will certainly help your kicks but I'm not sure it will necessarily solve your issue of pain.
As I understand it, you are trying to increase the height of your side and RH kicks to above-waist height, without pain, yes?
I will need more information before I can give you advice on this.

To satisfy your curiosity:
Have you seen improvement in individuals who start ballet and cannot achieve first position but after time and practice can perform one comfortably?
Yes. Incidentally, the "turnout" is not only necessary for first position in ballet, but for the *entire* discipline. Every position, pose, and movement done in ballet is done with the legs externally rotated to the maximum degree possible (ideally 90 degrees from the medial plane of the body, or what would be 180 degrees across both feet in first position), 100% of the time.
In any case, I await your reply, so we can get to the bottom of this and I can hopefully help you out. At this point what it looks like you're missing is the relationship between pelvis, standing leg, and working leg; because that rotation can change depending on the movement of all three pieces, depending on what's rotating what. But I want to get some more details before I go into it in depth.