I'm really perplexed by what is going on in megillas Rus. In chapter 3 Rus and Boaz keep talking about Boaz being a גֹאֵל, but גֹאֵל of what? Boaz is the uncle of Machlon and Kilyon and as such he doesn't have an obligation to do yibum (Yevamos 17b). So why the use of גֹאֵל in that conversation, why not just talk about plain old marriage?
Then, in chapter 4 גֹאֵל is used to describe redeeming an ancestral field. That makes sense to me, but then suddenly in pasuk 5 we read:
וַיֹּאמֶר בֹּעַז בְּיוֹם קְנוֹתְךָ הַשָּׂדֶה מִיַּד נָעֳמִי וּמֵאֵת רוּת הַמּוֹאֲבִיָּה אֵשֶׁת הַמֵּת קָנִיתָ לְהָקִים שֵׁם הַמֵּת עַל נַחֲלָתוֹ: And Boaz said, "On the day that you buy the field from the hand of Naomi and from Ruth the Moabitess, the wife of the deceased, you have bought [it], to preserve the name of the deceased on his heritage."
This doesn't sound like any field-redeeming גֹאֵל transaction I've ever heard of. How is Rus involved in this land sale? And how is Boaz able to add in these conditions? If Naomi is really selling the field why isn't she having a conversation directly with Mr. גֹאֵל (Ploni Almoni)?
Then it gets even more difficult. The pasuk (7) sounds like it is talking about chalitzah, but also about monetary transactions
וְזֹאת לְפָנִים בְּיִשְׂרָאֵל עַל הַגְּאוּלָּה וְעַל הַ תְּמוּרָה לְקַיֵּם כָּל דָּבָר שָׁלַף אִישׁ נַעֲלוֹ וְנָתַן לְרֵעֵה וּ וְזֹאת הַתְּעוּדָה בְּיִשְׂרָאֵל: Now this was the custom in former times in Israel concerning redemption and exchange, to confirm anything, one would remove his shoe and give [it] to his fellow, and this was the attestation in Israel.
So does גֹאֵל mean marry, redeem a field or both, and how and why does it seem to be used in these confusing ways in the narrative?