QFT? I'm thinking quite "freaking" true, but not sure.
I suppose I'd ask what is the scope of your paper? Is it to be one of definition (i.e. what defines religious (for that matter terrorism too) terrorism?) or is it to be one of "application" as you seem to suggest above (i.e. the why's and the how's)?
The psychology aspect is interesting but I don't know that there has been much pertinent or really scientific research on that topic, but you should ask Jay since he's the resident Psych.
As for the second question: this could also be very interesting but may also be a very depressing process. I imagine in order to successfully complete this research, you'd need to look up several attacks and where they were and also when. Keep in mind that the United States has not had as many terrorist attacks as other countries have had.
Lastly, the term "religious terrorism" confuses me a bit but only because I'm an English major and can see several different meanings of that someone nebulous phrase. Is it terrorism of religion? Is it terrorism with religious motives (i.e. something like the jihad)? If you define religious terrorism in a certain way, that may narrow your focus down a bit. Lastly, the Spanish Inquisition (not Monty Python's version) might be an interesting topic to look into. Also, would the Holocaust count as religious terrorism or is that something different.
Tl; Dr: Try to define "religious terrorism." / If you're going for psychology, ask Jay as he should know. / In addition to the Crusades, what about the Spanish Inquisition and the Holocaust in which other religions besides Christianity were targeted and in which mostly one religion was targeted, respectively.