I don’t think he has small chakra reserves. The only reason he constantly ran low was because he had use chakra intensive shadow techniques to restrain his opponents. It takes a lot of chakra to physically hold ninjas in place.
Where did you read that he had low chakra reserves?
Estoy bastante seguro de que la manipulación de sombras del clan Nara es un Kekkei Genkai, así que el comentario de Shikaku ("Tienes un Kekkei Genkai") queda inválido en ese mismo momento