Who said to whom? (M'nachos 70)

Question

Bavli, M'nachos 70 amud 1:

בעי ר׳ אבהו שבולת שמרחה בכרי ושתלה וקרא עליה שם במחובר מהו כיון דמרחה טבלא לה כי קרא עליה שם קדשה לה או דלמא כיון דשתלה פקע ליה טבלא מינה אמרי ליה רבנן לאביי אם כן מצינו תרומה במחובר לקרקע ותנן לא מצינו תרומה במחובר לקרקע אמר ליה כי תניא ההיא לענין איחיובי מיתה וחומש דאי תליש ואכיל תלוש הוא ואי גחין ואכיל בטלה דעתו אצל כל אדם

In my own loose translation (based on Rashi):

Rabbi Abahu asked:

[Suppose] someone smoothed a stalk [of grain] in a heap [thereby passing it into a stage of tithing obligation], then transplanted it and named it [as t'ruma] while it was attached to the ground. What is the rule? By smoothing it, he made it tevel [i.e., obligated in tithing], and, when he named it, he made it t'ruma; or, perhaps, by transplanting it he removed the tevel state from it [so naming it t'ruma had no effect]?

The rabbis told Abaye:

If [by naming it t'ruma he in fact made it t'ruma], then we have a case of t'ruma attached to the ground, and tanaim taught "there is no t'ruma attached to the ground".

He told him:

That statement, ["there is no t'ruma attached to the ground",] was taught about the penalty of death or a one-fifth fine [for someone who eats the t'ruma who should not have. That is, it means not that there cannot be t'ruma attached to the ground, but only that there is never a penalty for eating t'ruma attached to the ground]. For if he detaches it and eats then it's not attached, and if he bends over and eats it [attached to the ground] then his view [that it's considered eating] is voided by everyone else's [and no penalty attaches].

1. Why did the rabbis tell their statement to Abaye? What does he have to do with anything?
2. The last statement is preceded by "He told him". Who told whom, and why?

Answer 1

Some context would help here. Earlier in the Gemara, Abayei discusses a somewhat similar case (Davidson Edition translation):

אמר ליה ר' חנינא בר מניומי לאביי עציץ שאינו נקוב מהו אי לא נקוב הא לא נקוב

Rabbi Ḥanina bar Minyumi said to Abaye: In a case of a flowerpot [atzitz] that is not perforated, what is the halakha with regard to separating teruma and tithes? Abaye replied: What is the difficulty here? If it is not perforated, this halakha is the same as that of any non-perforated flowerpot, i.e., the separation of teruma and tithes is required by rabbinic law.

דלמא חזר ונקבו קא אמרת

Abaye continues: Perhaps what you meant to say is that he subsequently went and perforated it. In such a case the question is whether one may separate teruma and tithes from the initial growth of the plant. Is the initial growth considered a separate entity, in which case one part of the growth requires the separation of teruma and tithes by rabbinic law and the rest by Torah law, and therefore one may not separate from the initial growth? Alternatively, perhaps the initial growth is nullified by the subsequent growth, which would mean that the obligation of teruma and tithes applies to the entire plant by Torah law. Consequently, this obligation can be fulfilled by separating teruma and tithes from the initial growth of the plant. This would be similar to Rabba’s dilemma with regard to an ear of grain that is replanted.

הכא חדא זריעה היא איחבורי הוא דקא מיחברא ועולה התם שתי זריעות נינהו

Abaye explains that the two cases are not comparable. Here, in the case of the non-perforated flowerpot which was subsequently perforated, it is one single sowing. Therefore, although the original growth occurred while the pot was not perforated, since it is now perforated, the plant is considered attached to the ground and it rises and grows from there. Consequently, the obligation of teruma and tithes applies to the entire plant by Torah law. There, in Rabba’s dilemma involving the replanting of an ear of grain, there are two distinct sowings. Therefore, there is room to debate whether or not the additional, second sowing is part of the original, first sowing.

Based on the above, Abayei would hold that one can take Terumah off from the initial growth of the plant. Therefore, Abayei would understand the answer to Rav Avahu's question to be that it would be terumah while it was still attached to the ground. Meaning, your explanation of "Im Kein" is incorrect, and should read (added parts in italics):

The rabbis told Abaye:

If [according to your opinion by naming it t'ruma he in fact made it t'ruma], then we have a case of t'ruma attached to the ground, and tanaim taught "there is no t'ruma attached to the ground".

For your number 2, I see that the Chavrusa Gemara changes the text to אמר להו, "he said to them", which would be Abayei to the Rabbis. However, as pointed out by doubleAA, there is no manuscript evidence to support this in Dikdukei Sofrim. Sefaria simply translates it

Abaye said to one of those Sages

which is the clear meaning from the context.