I edited your second set of sentences by adding " ' " to the numbers so they are not confused with those of the first set.
The rule is that the determiner of the second noun (let's call it "the possession" as opposed to "the owner" represented by the first noun) can only be omitted when it is a definite or a zero article unless there is a numeral in the owner. That is the case with your sentences (4) to (6):
4 I guess these are an ancient man's weapons.
5 I guess these are a big man's shirts.
6 I guess this is a giant mouse's tail.
4' I guess these are (the) weapons of an ancient man.
5' I guess these are (the) shirts of a big man.
6' I guess this is the tail of a giant mouse.
The problem with your sentences (1) to (2):
* 1 I guess this is two women's house. (wrong)
* 2 I guess this is three boys' house. (wrong)
is that they do NOT mean:
1' I guess this is the house of two women (also: the two women's house).
2' I guess this is the house of three boys (also: the three boys' house).
If this is what you want to express:
- I guess this is a house belonging to two women.
- I guess this is a house belonging to three boys.
then you can restate (1) and (2) as follows:
1'' I guess this is a two women's house.
2'' I guess this is a three boys' house.
As regards sentence (0):
0 I guess this is one man's shirt.
I don't think it can mean: I guess this is the shirt of one man BUT I guess this is a shirt belonging to one man OR I guess this is one shirt belonging to a man.
As regards sentence (3):
3 I guess this is some boys' house.
I find it to be correct to mean:
3' I guess this is the house of some boys.
3'' I guess this is some house owned by boys.