1. Yes. coz DOL will think that the new comer can get the experience needed from ur current company. No need to give u PR
2. 前同僚,教授个人的类似推荐信之类 is fine (I did that way). No need offical ones
3. It is very important (my lawer told me). So some key word must appear on those letters ( I asked my co-worker to write a letter twice)