Grammar is not my strong field, but I can try to give you the following explanation and I hope it will help you understand the concept better :)
“有一天” can also be used in a future tense. Am I right?
Yes (sort of-->). The immediate example (shortest) I can think of is "总有一天" which can be translated as "someday eventually."
#2 & #3 有一天他来我家看我。
Can this be translated: "One day he'll come to my place to see me."?
No. This sentence can't be translated into "one day he'll come to my place to see me," however, all you need is one more character - 会。 So it becomes 有一天他会来我家看我。 However, I do want to mention that it sounds a bit awkward. A more natural way to say this sentence would be 总有一天他会来我家看我 (which means he will come to my place to see me eventually) but that changes the tone of the sentence. But, it is what you are looking when you asking for the expression "a certain person will eventually come to see me."
Just now happened upon one more example: 两个月以后我去看他们。
Again, the book translates this in past tense: "I went to see him 2 months later"
But can't it be translated as "I will go see him in two months time (after two months)."?
This one is a bit ambiguous to me so I will leave this question for someone with better grammar knowledge to help you out.
To accurately translate as "I will go see them in two months," it should be 两个月以后我会去看他们。 Written this way, there is no ambiguity in the sentence.
I hope this helps! 加油 :)
The following 2 links provide additional examples that might help you better understanding the concept:
On 总有一天： http://www.nciku.cn/search/en/examples/%E6%80%BB%E6%9C%89%E4%B8%80%E5%A4%A9%EF%BC%8C