I'm not sure I have a definitive grammatical answer, but in my experience as a native American English speaker, the "didn't" variant is more correct and natural. Saying
I haven't heard from him.
implies that although you have not heard from him yet, there is some expectation you might hear from him in the future.
Whereas
I didn't hear from him.
is strictly talking about what is in the past. By using
I didn't hear from him until now.
you are adding contrast between the past and the present.
I suppose "I haven't heard from him until now" might be ok, but it seems like the "until now" (aha, something has changed!) conflicts with the hopefulness/tentativeness of "I haven't heard from him" — how can you still be hopeful if you already know that the situation has changed?
re: "until now" vs. "till now" vs. "up to now":
"till" is an informal variant of "until". (although The Free Dictionary says that till came before until historically) If you say "up to now", people will understand you, and I don't think it is grammatically incorrect, but it is somewhat unnatural-sounding. I think the reason is that "until" is such a common preposition and has a very good match for this situation, that alternative forms don't seem right.
Hope this helps!
As a native speaker, I would not necessarily understand
I have got a family
to mean
I have a young family.
in your example got is an intensifier emphasizing the fact that you have a family or any age. It's possible the person who told you this was themselves young and had a young family.
"I got a car."
Can mean "Recently, I acquired a car." depending on additional context, but "I have got a car" does not. Using got this way is very idiomatic which is usually not used when describing a family, since one does not go out and "get a family" like one goes out and "gets a cat".
Best Answer
The construction Would you care for [some] X? is a kind of "frozen form" largely restricted to extremely polite / formal contexts. Usually where the speaker (a restaurant waiter, for example) is addressing someone of higher social status). X can be either a noun (something being offered) or an infinitive-based verb clause (an activity being proposed)...
Note that the first three are all servile / polite offers (speaker will provide you with coffee, tea, or an outside seat if you want it). But #4 is effectively a request - a stylized / polite way of saying Please follow me.
Also note that unless he was being deliberately facetious, if the addressee didn't want coffee, he probably wouldn't reply...
...because the negated statement I don't care for X is a stylized / dated way of saying I don't like X (ever, I'm not just refusing the current offer). And the non-negated Thank you, yes. I [do] care for coffee simply isn't something native speakers say.
The primary difference between Would / Do you care for X? is we use would in the context of polite / formal offers and requests, where care for means want / like. We only normally use do in contexts where care for means to look after / tend to the needs of (or sometimes to feel deep affection for, but that "romantic" sense is becoming increasingly dated today).