Thank you for your kind words! It’s good to see a fellow enjoyer of old-school shooters here!
Learning how to wall jump with thrust kicks can indeed be tricky. How I always do it is by jumping while facing the wall I want to wall jump from, then look downwards so that the camera direction is at a steep angle relative to the wall, then kick. This usually maximizes jump height, but I get that it takes some getting used to.
(In case you need visual reference, on the game’s page there’s a full walkthrough in which I perform that particular jump to get to the red door)