With "already", they mean the same thing. The function implied by "already" is "a completed action in the past with present result". The difference between the two types is Americans tend to prefer the simple past version, while everyone else --including Canadians-- prefers the present perfect.
The only exception is with 5. &...
Both options are grammatically correct.
A rough heuristic for which option to choose is shown below. This is not a rule, just a guideline. Thanks to @gotube for the comment about tenses and @stangdon for clarifications.
Option 1 is the present perfect tense. Use option 1 if he's still in the US. "He's spent at least a year in the US thus far, so he ...
At the time he was thinking, they had already finished carrying the TV, but he was thinking about the time that he saw them, and at the time they were in the process of carrying the TV. The best way to describe his thoughts is to use past continuous:
The two men were thieves and the TV they were carrying was his TV!