"What have you given him?"
Translation:Τι του έχεις δώσει;
That was how I learned it in 1995 and also how it is spelled in my 1995 edition of Triandafyllidis's Neoelliniki Grammatiki.
It only talks about replacing dropped sounds with apostrophes but does not mention omitting the space as well, and the examples are like σ' εμένα and μου 'φερε (paragraphs 41, 42).
Have the rules changed since then?
So you're saying that instead of just the dative pronoun (as τού for example), indirect objects can also be expressed with σε + demonstrative pronoun (σ'αυτόν, σ'εκείνην) or noun (στον άνθροπο, στις γυναίκες);
I don't recall a lesson specifically on indirect objects (or objects in general for that matter.) But I started with the old tree, so I can't check back.
I think that τού is correct, particularly if there can be an ambiguity with a preceding possessive, which has the same form), as in Η ματέρα του τού έχει δώσει ένα βιβλίο. Here there is no ambiguity, so I'm guessing that the accent is optional, or at least only required by Greek teachers, and not used in daily practice.