Will the repentance of a sorcerer who profanes the Qur'an and abuses the Divine Essence and the Messenger (peace be upon him) be accepted, or is he among those who despair of Allah's mercy, by analogy with the story of Abd Allah ibn Abi Sarh?

What the questioner mentioned is correct: sorcerers draw closer to devils through disbelief and polytheism, and in return, the devils fulfill some of their desires. This is an act of disbelief, for the ultimate state of a sorcerer is that of a disbeliever. If a disbeliever repents, Allah accepts their repentance and forgives their past sins. As for what was mentioned about the story of Ibn Abi Sarh, it is an issue related to accepting or rejecting the repentance of a zindiq who promotes innovation. There is disagreement regarding whether such repentance averts worldly punishment, but no one has claimed that if a zindiq or a sorcerer truly repents between themselves and Allah, Allah would not accept it from them.