the answer that joan gave does give an approximation of where the angles are, but the more you go from centre the less accurate it is, at the end to get a perfect relation between the exact angle and the exact equivalent in pulse width I used a simple rule of 3:
I basically put my motor in the exact centre (in my case 1435), then I kept manually adding ...
My initial problem seems to be irrelevant. I did not understand what was meant by "throttle" which is more of an RC jargon misunderstanding than it is an issue with raspberry pi. (If you're looking for an answer this link shows it pretty well.)
Sorry for being off-topic! Sometimes it's hard to know when you are working from little experience. :)