What is the interpretation of the destructive thoughts that cross my mind, such as "If there are jinn, why do I not see them?", and the feeling of constriction and darkness in my chest for seven years? Does this indicate hypocrisy?

What you are experiencing of satanic whisperings is evidence of faith, not hypocrisy. The solution is to seek refuge in Allah from them and turn away from them. Not everything that exists is visible, and we believe in things we have not seen due to trustworthy reports. The feeling of constriction is also from Satan, and its cure is to seek refuge in Allah and turn away from the whisperings, while increasing the recitation of the Quran and remembrance of Allah (dhikr), and associating with righteous women.