Tosafos proves that geirim were not included in arvus. Based on this it should come out that the halacha that allows one to make kiddush and blow shofar for another even after being yotzei himself should not apply to a ger. I am troubled that the exclusion of a ger from arvus isn't mentioned by the halachos where we use arvus to be motzi others such as kiddush. Is anyone familiar with a source?
(I found an article from my brother R' Aryeh, where he quotes R' Shternbach who says a drush to distinguish between arvus for communal responsibility for them, and arvus on the personal level to be motzi them. However, I find this very hard to swallow).