1. Tosafos asks that if there is a retzuah seperating galil from jerusalem, how can one be oleh regel and still be tahor? Hagahos Ransburg says that he can get there by putting a board on an ox. Why can't we use that trick to get wine to jerusalem? He answers that it is similar to Eiruv in a cemetery where the maharsha explains that using this trick is not considered access to the eiruv since it is not a common way to travel. I don't understand the connection! By eiruv we don't consider this method as having "access" since it is not a common means of travel, but if someone shows up with wine in jerusalem that they brought from gallil on the back of an ox, why is that not acceptable for nisachim?
2. Rashi explains that if the 2 brothers split wheat and the chaver takes the tahor and give his brother the tameh, that is fine. But he cannot "sell" the tameh barley to his brother, to ensure that he receives the tahor wheat, since he is providing him with an issur and is violating lifnei iver. Why in the first case is it not lifnei iver? Had the chaver taken the tameh and thrown it out his brother would take the tahor and avoid any issur, so by the chaver taking the tahor he is causing (trei avri d'nahara) his brother to do an issur!? We see from here a big yesod. The issur of lifnei iver is to pass wine to a nazir since you are passing to him issur. But if there is one cup of wine and one of water in front of the nazir, one may take the water even though they will be causing the nazir to drink the wine. It is only lifnei iver to pass him the issur, but one may take the heter and thereby cause him to do his own issur.
3. The migu in our gemara is since we believe him for the kodesh in this barrel we automatically believe him for the terumah in it since they are 1 unit together in a barrel. Similarly, since we believe his body is tahor for pesach we beleive him for terumah since his body is 1 unit. Why does rashi have to explain the migu that to beleive him on the kodesh and not teruma is "degrading for the mizbeiach", just say that it is one unit that can't be split?