Three Forms of Redemption in Megillat Ruth

In the fateful nighttime encounter on the threshing floor, Boaz is startled to find someone lying at his feet:

And he said, “Who are you?” And she replied, “I am Ruth, your maidservant. Spread your wings (khenafekha) over your maidservant, for you are a redeemer.” And [Boaz] said, “…And now, even though truly I am a go’el, there is a go’el who is closer than I. Lie here tonight and in the morning, if the redeemer shall redeem you, good, but if he shall not desire to redeem you, I myself shall redeem you, I swear by God. Lie until the morning.” (Ruth 3:9-13)

What is the meaning of Ruth’s request that Boaz spread his wings over her, and her statement that Boaz is a redeemer? Targum, Rashi, Ibn Ezra, and Ramban assume that Ruth’s request for Boaz to spread his kanaf over her is a request for marriage. 

Nevertheless, it is less clear what Ruth means when she states plainly, “For you are the go’el.” In what way does this relate to Ruth’s previous request? Is it also a bid for marriage, which Ruth terms her redemption, or does this refer to Boaz’s ostensible duty to buy Naomi’s property?