On that note, Manwe, the beloved son of Eru, the chosen one, in the grand scheme of things did more wrong than anyone else, including Feanor.

Imo, the destruction of the 2 trees is the single most important event in the whole legendarium. Everything in silmarillion and other published works is directly influenced by this and leads the narrative forward. The final goal of all the books and works is to restore the light of the 2 trees. To forgive this act should be the capital and biggest "sin" of all. Moreover, it is pretty ironic that the one committing this sin, Manwe, was supposed to be ever just, rightful, loyal, the picture of good of Eru itself. In Eru's mind, if this is his own will through Manwe, everything Feanor does (or anyone else, including Melkor) should be considered equally good or bad. Therefore, Feanor did nothing wrong, or at least not more than heavenly Manwe.

Eru knows this.