It was shown, in X-Men Origins: Wolverine, that from their childhood days to 1975, Wolverine and Sabretooth were together. In X-Men: Days of Future Past, when Logan travelled through time back to 1973, why wouldn't he seek help from Sabretooth?
For one thing, Wolverine was kind of busy and working on a schedule. It would have been difficult to go to the trouble of tracking down Sabretooth, particularly if Victor was on a mission for William Stryker at the time. He could have been literally anywhere on Earth, and Logan, having suffered serious memory loss at the end of X-Men Origins: Wolverine, and likely still not regaining all of his memory even by the time of the film The Wolverine, may very well not have remembered where Victor was at the time.
You must also remember that Victor and Logan weren't exactly on good speaking terms by the time the present-day events of X-Men: Days of Future Past took place. Victor had murdered several of Logan's friends, attempted to murder several others, broken Logan's original bone claws, worked with Stryker, attempted to kill Logan, joined up with Magneto, fought the X-Men on several occasions, and shown a severe bloodlust which included at least one attempted rape. It is highly unlikely that this is the sort of person Logan would turn to for help, even if most of Victor's crimes were still in the future.
Because he does not remember where Sabretooth was. Maybe Sabretooth was right now in China meanwhile Wolverine in America. Wolverine had no time to "search" Sabretooth.