The first should be -100% = 0%, 0% = 50%, +100% = 100% and 1:1, or -100% = -100%, 0% = 0% and +100% = +100%. At least my limited experience with HOTAS throttles is how I've seen it. Between the game and Windows you should have these options. And it also depends on if you want to have reverse throttle as an option below center all the time, or use a toggle switch to reverse your throttle inputs and use -100 as 0 throttle and +100 as full throttle (what I prefer, more precise).
Hopefully almost a week later you've found an answer to your question, sorry I am not able to better answer it!