Velocitous

Depends on what you mean by this. If you what you mean is that you are interested in working with some faculty in a different subfield, that's totally fine (e.g., I want to study bureaucracy in Japan using network methods - express interest in CP scholar who does political parties in Japan + Americanist who does US bureaucracy + IR scholar who's an expert in network statistics). If you're trying to say that you want to primarily work with someone who works outside the subfield you claim as your main area, then that should raise red flags in your head. If you want to work on a topic, which you think is IR, but all the people working on it are comparativists, then you're probably (a) actually a budding comparativist or ( misunderstanding something. Either way you need to evaluate what your real interests are and where they fit into the discipline.

Don't bother with WUSTL. From their website: "We have active research groups in American politics and institutions, comparative politics, international political economy, positive and normative theory, and political methodology". And that's an exhaustive list - you really can't do security stuff at WUSTL and it would be unwise to try.

If I'm understanding your question right, you're asking whether you should re-take calculus so that it will show up differently on your transcript? I hope that reading this rephrasing will be sufficient to convince you not to. People understand what "math for economists" implies, and if you're especially concerned, have a letter writer mention it.

It never hurts to try. If you really want to be a political theorist, then spending a few hundred dollars on application fees is not some giant loss. It sounds like you have a really strong connection with your political theory professor, and this can go a long way (particularly if he's relatively well connected). A good letter from him that explains your low GPA, talks convincingly about your strengths, and assures committees about your potential could be a game changer. The low quant GRE issue is harder to finesse than the GPA one. If you think that studying and retaking could bump that up, then it's imperative that you do so. Many faculty use the math GRE score as a hard cutoff and won't read any further on a file with a score in the 27th percentile. If that's the really the best score you can achieve, then you may find that you have limited options, but if you're hitting the 96th percentile on verbal, then it sounds like you have the intellectual horsepower to take on the math section if you buckle down and study. Finally, many applicants with a low GPA go into a masters degree program, where they can excel, get good grades, and prove they're up to the challenge. You should consider this option.