In the appData.JS you only have to change the first three ":" to ";" and the last one. the ones that are wrong are underlined in red. This should probably be list as a bug as it happens for every app I create with zipapp

I managed to get an almost full screen experience by changing the videodetail.css file.

#videoDetailInfo {
  position:absolute;
  left : 695px;
  top:0px;
  height:calc(100% - 142px);
  width:340px;
}

#videoDetailDescriptionWrapper { 
  padding:0px;
  width:320px; 
  color: rgb(128, 128, 128);
  height:100%;
  column-width:340px;
  column-count:auto;
  column-gap:20px;
}
#videoDetailDescriptionBackground {
  background-color: rgba(255, 255, 255, 0.5);
}

#videoDetailDescription {
  font-family:'Segoe UI'; /*font-family*/
  white-space:pre-line;
  word-wrap:break-word;
  padding:10px;
}

#videoDetailPlayer {
  width:600px;
  overflow:hidden;
}

You may need to experiment with the video detail js and css file.  The changes were to make the  video detal player width 980px and move the videodetailinfo to left: 1100px