Does swallowing one's saliva after water droplets have touched the lips invalidate the fast, even if the mouth is not wiped?

Your fast is not invalidated by swallowing saliva, even if you do not wipe your mouth after spitting. Nor is it invalidated by the presence of water droplets on the lips, unless you intentionally swallow them. As for the acceptance of the fast, that is a matter of the unseen, and you must perform it correctly with sincerity to Allah and hope for acceptance.