Film

2) Yes the lack of love potion does change the whole idea of Tristan and Isolde. In the film their love is portrayed as true love as apposed to the love in the text which is only brought on by the love potion. Although it does not justify their love it does give more credit to them as betrayers of the king. What they do in the film is more cruel in that they could control their love, save the kingdom, and pay their loyalties to King Mark. The film portrays Tristan and Isolde as the bad guys, in the text God and the author are on their side.
5) The barons are portrayed as better people in the film. In the text they are conniving men who worked only for their own gain. In the film they do seem to be working in favor of the king. Although the plot to catch Tristan in the act is somewhat slimy, I feel that the director shed a kind light on them. In this case, the author did not have a say in who the actual evil men were, and the barons are better men striving to hold the structure of the alliance.