7 ,8 days too short for the internery you planned
you cant enjoy full
i suggest you to plan tirupati balaji next time and go madurai,rameswaram,kanyakumari and back to howrah for this few trains sufficient like coromondal upto chenna and chennai to madurai and from there rameswaram by train or bus/taxi and from rameswaram kanyakumari is very short distance and return u can plan to return to howrha instead of balaji tirupati