1. There are many state and federal laws which prevent these political parties from being on the ballots and/or debates. So yes, there is plenty of political power against the proliferation of these parties. Although the winner takes all voting system also perpetuates a binary division of political beliefs.
2. Not necessarily. Coalitions are a notable feature of multiparty politics. More disagreements will be resolved because say Republicans and Libertarians can overcome Democrats on an issue they both agree on but Democrats disagree with, and likewise Democrats and Libertarians vs. Republicans, and likewise Republicans and Democrats vs. Libertarians.
1. It costs $1000 to get your name on the ballot for the New Hampshire Presidential primary. That's pocket change to any serious candidate.
2. With more parties you'll see more instances of Republicans vs. Democrats vs. Libertarians vs. Greeners vs. etc... Heck,the Republican party is divided right now between traditional Republicans and the right-wing Tea Party crazies like Ted Cruz. Republicans can't even come together to solve some of our nation's problems.