How to understand Euler angles from cv2.decomposeProjectionMatrix?

Question

I have been searching the internet for hours on some documentation on how to understand the Euler angles returned by cv2.decomposeProjectionMatrix.

My problem seems simple, I have this 2D image of an aircraft. I want to be able to derive from that image how the aircraft is oriented with respect to the camera. Ultimately, I am looking for the Look and Depression (i.e. Azimuth and Elevation). I have corresponding 3D coordinates to the 2D features selected in my image - listed below in my code.

# --- Imports ---
import os
import cv2
import numpy as np

# --- Main ---
if __name__ == "__main__":

    # Load image and resize
    THIS_DIR = os.path.abspath(os.path.dirname(__file__))
    im = cv2.imread(os.path.abspath(os.path.join(THIS_DIR, "raptor.jpg")))
    im = cv2.resize(im, (im.shape[1]//2, im.shape[0]//2))
    size = im.shape

    # 2D image points
    image_points = np.array([
                    (230, 410),     # Nose
                    (55, 215),      # right forward wingtip
                    (227, 170),     # right aft outboard horizontal
                    (257, 71),      # right forward vertical tail
                    (532, 96),      # left forward vertical tail
                    (605, 210),     # left aft outboard horizontal
                    (700, 283)      # left forward wingtip
                ], dtype="double")

    # 3D model points (estimated)
    model_points = np.array([
            (    0., -484.1, -18.4), # Nose
            (-758.1,  872.4, -15.9), # right forward wingtip
            (-470.3, 1409.4,  -7.9), # right aft outboard horizontal
            (-287.3, 1040.2, 323.3), # right forward vertical tail
            ( 287.3, 1040.2, 323.3), # left forward vertical tail
            ( 470.3, 1409.4,  -7.9), # left aft outboard horizontal
            ( 758.1,  872.4, -15.9)  # left forward wingtip
            ], dtype="double")

    # Estimated camera internals
    focal_length = size[1]
    center = (size[1]/2, size[0]/2)
    camera_matrix = np.array(
                             [[focal_length, 0, center[0]],
                             [0, focal_length, center[1]],
                             [0, 0, 1]], dtype = "double"
                             )
    # Lens distortion assumed to be zero 
    dist_coeffs = np.zeros((4,1)) 

    # Solving for persepective and point    
    _, rvec, tvec = cv2.solvePnP(model_points, image_points, camera_matrix, dist_coeffs, flags=cv2.SOLVEPNP_ITERATIVE)

    # Rotational matrix
    rmat = cv2.Rodrigues(rvec)[0]

    # Projection Matrix
    pmat = np.hstack((rmat, tvec))
    roll, pitch, yaw = cv2.decomposeProjectionMatrix(pmat)[-1]
    print('Roll: {:.2f}\nPitch: {:.2f}\nYaw: {:.2f}'.format(float(roll), float(pitch), float(yaw)))


    # Visualization
    # Points of interest from the nose
    poi = np.array([(model_points[0][0], model_points[0][1]+1e6, model_points[0][2])])     
    poi_end, jacobian = cv2.projectPoints(poi, rvec, tvec, camera_matrix, dist_coeffs)

    p1 = ( int(image_points[0][0]), int(image_points[0][1]) ) # nose
    p2 = ( int(poi_end[0][0][0]), int(poi_end[0][0][1]) ) # poi

    # Show the 2D features
    for p in image_points:
        cv2.circle(im, (int(p[0]), int(p[1])), 3, (0,0,255), -1)

    # Line from nose to projected point
    cv2.line(im, p1, p2, (255,0,0), 2)

    cv2.imshow("Output", im)
    cv2.waitKey(0)

Below is my output image, as you can see the point projected aft does not seem to follow the centerline. I'm not entirely certain that my code is working as I intended so please feel free to offer helpful inputs.

Thanks in advance!!