~派 means "school" (of thought), and is widely applied when setting up "sides" of an argument. e.g. for 卵焼き you have 甘い派 vs. 塩っぱい派
For 理性派 the opposite seems to be 感性派 (rational vs. emotional?)
2. Which bit are you stuck on? 走り needs context, but could literally be "running", as in, he's good at/a gifted runner.
本人 means "the person himself", usually the subject of a conversation already brought up.
本人から聞いたよ = I heard from him/her directly (about himself/herself) (i.e. not from a third party).
本人は否定しています = He/she (the person against whom some allegation was made) is denying it.
(transactions for which proof of identity is required - e.g. 本人 = the owner of a bank account, for example)