Learn English – When to place “already” at the end of a sentence

Yes, "end" as used there as an active verb. Combined with the helping verb "would", it expressed the hoped-for (but at that time not yet realized) action of slavery ending (stopping, ceasing to exist).

Compare: "This class will end at 11am."

By the way, Lincoln had no illusion that slavery would end "when he gave the Gettysburg Address". The Civil War was far from over. Rather, when he gave the Gettysburg Address (and before, and after) he hoped that slavery would end sometime soon.

First off, we must remember that "though" can be used as a conjunction and adverb, whereas "although" is a conjunction; it's never an adverb. So "although" and "though" are only interchangeable when they are used as a conjunction.

As a conjunction, "though" is much more common than "although" in speaking.

When used as a conjunction, "though" or "although" can be used at the start of a subordinating clause whether this clause comes before or after a main clause.

As for the "though" as an adverb meaning however, you usually use it at the end of a sentence.

In the sentence "It was a good game though" presented by the OP, the "though" has been used as an adverb.