In a large bowl, vigorously whisk the egg yolks and 1 cup canned cream of coconut until the mixture is very pale, 1 to 2 minutes. Whisk in the milk, 1 cup cream, the rum, salt and the vanilla bean and seeds.
In the bowl of a stand mixer, beat the egg whites on medium until soft peaks form. Add 1/4 cup sugar; beat to form stiff peaks. In 2 batches, whisk the whites into the yolk mixture. Cover; refrigerate 4 to 6 hours.
Before serving, in a medium bowl, beat the remaining 2 cups cream and 1 tbsp. sugar until soft peaks form, about 2 minutes. discard the vanilla bean. Gently whisk the eggnog; ladle into cups. Garnish with coconut sorbet and toasted coconut.