Is the Attic rho similar to that French 'r'?
The Attic "rho" should not be pronounced like the French "r". Indeed the french "r" is pronounced in the back of the throat whereas the greek "rho", should be pronounced like the modern greek one and like "r" in spanish and italian (and therefore latin), i.e. it has to be rolled. The french "r" used to be pronounced so untill the XVIIIth century. At this time, people at the king's court started pronounce it the way we do it now for they thought the rolled pronounciation sounded to "rural"
. Yet, there are still people in France (esp. south-west) who roll their "r".
As for the the rest of your question (dealing with pronounciation only), only "khi" is to be pronounced in the back of the throat. We are taught in the uni. that it should sound more or less like the german "ich
" (i.e. a retroflex consonant) which is the way the modern greek pronounce it. As for "thêta" and ""phi", i prefer the modern greek prononciation rather than the erasmian one which makes no difference between "thêta" and "tau".