Sorry about your illness and hope you are feeling better, Zambelli.
A cellphone video *might* help, but go ahead and post that .ahf film of your flight here. Everyone on the board can download it and look at it, and I think that allows reviewers to see engine settings and airspeed as you fly.
You've ruled out computer hardware by getting a new computer. Ruled out problems with the stick by performing the tests both I and Fugitive described, and noting proper behavior of the stick in both tests, and by trying a different stick. You've ruled out problems with the game installation by re-installing the game on your old computer, and by installing a fresh copy of the game on your new computer.
Ruling out all these other factors, it sounds like you could be experiencing an accelerated stall. The ahf should help someone figure out whats going on.