I agree that they could've introduced Mark better, I'm not saying they couldn't have.
As for the dairy farm, if you remember the episode 2 preview they already had the farm in mind. They had to put it in. I guess in your view they sort of shot themselves in the foot. Same with the motor inn scenes. If they were going to go into how Mark became part of the group, a cut scene wouldn't do it, it would've required a whole new sequence to be added to the episode, and they just did not have the time I guess.
As for the gripe about the choices. It's hard to make a game that makes you feel like 100% of your choices will have a major effect in every episode. If the game was truly tailored like that to each and every player, it would be totally impractical. Having a game play out relatively similar for each player makes it easier for the team to go from one episode to the next. Just think about all the work that has to be done for taking in account for saving Carley or Doug. Those scenes have to done twice, each with one of those characters.