Can you please help me understand the Maharsha's pshat in Rashi (the Maharshah is located on Rashi on the mishnah but explains both Rashi there and Rashi on the gemarh's question on 38b two lines from the bottom "Eimah bemaiy...")

Thanks

Here's where I'm stuck:

First, I'm not looking for pshat in Rashi according to Tosfas, Rashba and Ritva, who use a different approach, i.e., they explain that R' Eliezer ("R/E") was only suggesting taharah from zivah bemaiy zivah (during the 80 days, where she is carrying another vlad)according to the Rabanan's shitah, but R/E himself would hold (i.e., even at the "hava minah" stage when explaining his view at the mishnah and not just at the "maskanah" stage when the gemarah challenges his view) that she is tameh through and through- i.e.,even for zavah, and not just for nidah (and this is what R/E means when he says tameh, stam, in the mishnah).

Rather, I need clarification in the Maharsha's mehalich in Rashi, which was that Rashi on the mishnah was saying that R/E himself, i.e., as an expression of his own view, was only metamah for nidah, but not for zivah.

This mehalach in rashi produces a question- why (38b two lines from the bottom "Eimah bemaiy...")the gemorah challenges R/E that he should hold that she is tahor for zavah (and tameh for nida)- for that indeed is precisely what R/E does hold!

The Maharsha answers that Rashi was saying that it was possible for R/E to hold this view (i.e., split between zavah and nidah) at the point of the mishnah, but at the later point (two lines from bottom), Rashi would be forced to say that R/E holds that even zavah is tameh (i.e, not split dinim of tumah), and thus, the gemorah's challenge (i.e., that the "din" s/b split according to R/E).

I need help understanding how the Maharsha learned that pshat in R/E was forced to be changed. I've discouted the possibilities I came up with as follows:

1.Now that Rava says "damah" in explaining R/E, it's clear that R/E holds that tumah applies even to zavah. Discounted as pshat in Rashi, since in the gemorah's question, Rashi explains explicitly that this question is founded upon the basis that R/E holds "dayo"- which is precislely what R/E held in the mishnah (explicitly)- so nothing has changed now- so that cannot explain the forcing factor to change our understanding of R/E.

2. The Maharsha is merely saying that by virtue of the gemorah posing this question, we see we must change our understanding as to what R/E holds. Discounted b/c the Maharsha has a chesbon as to why it logically makes sense to learn one way in R/E in the mishnah and why from a chesbon- R/E cannot be understood this same way later in the gemarah. To me, the Maharsha is not saying that this chesbon is a chesbon of: by virtue of the gemorah posing the question.

3 That the "dayo" R/E uses in the mishnah is different than the "dayo" he uses later, and then produce a sevarah as to why using the different "dayos' would force different understandings of R/E's shitah. Discounted- b/c R/E uses the same "dayo", plus don't know what that sevarh would be.

4. As mentioned, Tosafos two pshatim will not work for Rashi according to Maharsha's understanding of Rashi.

What then was it that was so clear to the Maharsha that Rashi was forced to change what could be our understanding of R/E in the mishnah to a different understanding a bit later in the gemarah?

Daniel Gray, Toronto, Canada