What is the authenticity of the Hadith which states that whoever recites Ayatul Kursi after every prayer will not be prevented from entering Paradise except by death?

The books of the people of knowledge mention that the meaning of "nothing prevents him from entering Paradise except death" is that if he dies, he will enter Paradise. The intention is that his soul will settle therein, or that "entering" refers to enjoying its delights immediately upon his death.

They also indicated that Ayatul Kursi was singled out for this virtue because it encompasses the fundamental principles of the divine names and attributes, oneness, life, self-subsistence (Qayyumiyyah), knowledge, dominion, power, and will.