Is there an explanation for why this chapter of tehilim was written according to the Aleph Bet, and why it skips the vav?
The Radak there explains that it was made in Aleph Bet order because of the happiness from his escape:
מרוב השמחה ששמח דוד בהנצלו עשה שירה זו באל״ף בי״ת
As noted in the comments by DanF, Radak notes that the vav line is included in the hei line of:
הביטו אליו ונהרו ופניהם אל יחפרו
This is not uncommon in piyutim, songs, and even tehillim, etc, see, for example the comments to this question.