Archaic meaning of 'procure' - 1615 UK

Question

Source: p 105, The Law of Contract, 5 ed (2012), by O’Sullivan and Hilliard

It is encapsulated in the difficult seventeenth-century language of Lampleigh v Braithwait (1615):

A mere voluntary courtesie will not have a consideration to uphold an assumpsit. But if that courtesie were moved by a suit or request of the party that gives the assumpsit, it will bind,
for the promise, though it follows, yet it is not naked,
but couples itself with the suit before [] and the merits of the party procured by that suit,
which is the difference.

This means, if A asks B to do something for him and later promises to pay for it or do something in return, A’s promise will be enforceable because it is supported by consideration, namely what B did at A’s request.

1. Am I right in guessing that Definition 2.1 applies? But how does it make sense for a suit to procure 'merits of the party'? What did I misinterpret?

2.1 = (archaic or Law) Cause (something) to happen:

2. What's the antecedent of which? Which 'difference' does it concern?
Is it whether a 'courtesie' has consideration or not?

Answer 1

(1) I think that procured in the quotation simply means "obtained" or "achieved." The crucial (and perhaps unexpected) meaning here is the one associated with merits. Here is the Black's Law Dictionary (1968) definition of merits:

MERITS. The word "merit" as a legal term is to be regarded as referring to the strict legal rights of the parties. [Citation omitted.]

So the phrase following the word naked in the quotation might be restated as follows:

but couples itself with the suit before, and [asserts or lays claim to] the strict legal rights that the party obtained by means of that suit,

(2) The word "which" near the end of the same sentence refers to the entire lengthy phrase "for the promise, though it follows, yet it is not naked, but couples itself with the suit before and the merits of the party procured by that suit." In effect, "which is the difference" amounts to saying "and that distinction [namely, the one detailed in the 'for the promise...procured by that suit' portion of the sentence] is the difference."