[ISSUE #1] MY TRUSTED SERVANT: (Trait)
When you reveal your force, you may reveal up to 3 additional characters, each of 150 points or less. After all of your opponents reveal their forces, you may choose one of those characters to add to your force.

Question:

1) I have been told by 3 players at a venue, that ig008 Thanos can choose a character from an opponents team and use it as his own.

When I read ig008 Thanos rules I saw that the [ISSUE #1] MY TRUSTED SERVANT: (Trait), is the only thing that could be interpreted in that way. I have not seen anything that could mean that ig008 Thanos can choose a character from an opponents team and use it as his own.

After reading that Trait I understand that Thanos can only choose 1 of the 3, 150points or less characters he (thanos) brings to the game, after every players reveals the characters they are going to use, is this correct?

Correct, you don't choose an opponents character, you choose one of your own 3. The point of it is to let you choose a potential silver bullet to your opponents team.

Follow-up question... is that character that you add to your force (whichever 1 of the 3 you choose) in addition to the point build, or does the servant character have to be included in the point build?

It is not included in your point total.