Concept of remoteness

Dear Teachers,

After talking english for half a year, I found that I have some question on the remoteness of the reported speech I make. Following are the question that elaborate my point.

1) Marriete: Did Bob tell James that he is his father?
2) Marriete: Did Bob tell James that he was his father?

From the above sentence, which one is correct? I kind of think that both are correct but I think that sentence 1 is better because it shows that it is a fact that Bob is James father. Howabout sentence 2? I can't decide which one I should use in my speech because I cannot differentiate the remoteness of the event relating to the past tense speech? Following are another examples:

Jaison: What did James learned in the trip?
3) Marriete: James found out that Bob is his father and Bob is the chairman of the company James is working for now.
4) Marriete: James found out that Bob was his father and Bob was the chairman of the company James was working for.

For former usage, I think sentence 4 would be used because all past tense consistancy. However, I kind of think that sentence 4 doesn't show the fact that Bob is still alive and is still is James's father and Bob is currently the chairman of the company.

If both sentence 3 and 4 can be used indistinctively, when will be the time where sentence 4 is more appropriate to use than sentence 3? 1 week after James' discovery? Or 5 years after James' discovery then we should use sentence 4 instead of sentence 3? I kind of confused in the remoteness of the event in order to change my speech from the current fact to total past tense speech just as shown by sentence 3 and sentence 4. I hope somebody could provide me with answer. Thank you.