It is stated Jesse has been living with the family for seven months. When he moves in in the pilot, it is stated Pam has been dead for three months, meaning as of this episode she's been gone for ten months. However, in the earlier episode Danny's Very First Date (1988), it is stated she's been dead for a year.
When Danny tells D.J. the truth about Jesse, his hand suddenly appears on her shoulder, then disappears. Then when he picks up the guitar, he puts a hand on the fretboard, but in the next shot this same hand is not touching anything.
When Jesse returns he stated that he drove 4 hours from Lake Tahoe. Although it's typically a 3 hour and 24 min drive from Lake Tahoe to San Francisco, it's possible that he was going at a slower speed due to conditions. In fact, he does mention driving behind a slow-moving truck on the way back.