How essential is the role of the server at Low Mass?  Isn't the peoples part to say the responses?

  Is the priest forbidden from saying Mass without a server?

Isn't the peoples part to say the responses?

I'm no expert on liturgy.  One of our priests trained me to serve the Low Mass.  I asked these same questions along the way, since I was not used to the TLM.  In particular, he said that in the history of the Mass, rarely have there been rubrics for the posture and activities of the people.  The Missals concern themselves with the action at the altar.  It is for this reason that one finds the wonderful diversity of devotional practices among people at a TLM.  

On a personal note, I find serving the Low Mass to be among the most rewarding experiences of my entire life.  I learned from the a little red paperback pamphlet which our chapel prints, it was not terribly difficult.  In addition, it was a bonding experience with my father, who had been a server in the 1940's, and through this bonding he began to question some of the problems in the NO and he began to seek out the TLM.  

We're a much more harmonious family now.  I give full credit for that to the TLM.