according to your explanation in (1) why is it safek hinuah lo yitol, it would seem that the torath haim qouting the rosh applies only when it is possible it never belonged to a yisroel but might be from emoriim but not if it definetely was shel yisroel and only safek aveida which would answer rava's case?
avraham bendavid, uk
The Imrei Maharshach indeed mentions such a difference (in Tosfos 26a, according to the Rosh).
All the best,
Yaakov Montrose