Does my retraction from donating charity to the orphanage due to the dishonesty of its custodians, and my giving it directly to other orphans, count as a retraction of charity, which is likened to "a dog that vomits and then returns to its vomit"?

If it is possible to give the money directly to the orphans, then do so. If it is not possible and you believe the charity will not reach them, then give it to other orphans or the poor. This is not considered a retraction of a gift, which is prohibited.

Officials should monitor the affairs of orphans, and one should not abbreviate the salutation and peace upon the Prophet, peace and blessings be upon him, in writing.