All that vs. everything that

Why can one not say "I believe all he said"?

In some contexts, "all that" and "everything that" mean much the same thing:

"I'll take all (that) you can give me" ~ "I'll take everything (that) you can give me"

"All (that) I've worked for is lost" ~ "Everything (that) I've worked for is lost"

In other cases, "all that" has the special sense that "all" is a small amount: that one is not asking for much, that one does

Cool. So is there a change in meaning then between
* "I believe everything he said." and
* "I believe all he said." ?

Which phrase would you prefer to use?

I believe everything he said./ I believe all he said.-- There is no difference in meaning as these stand.

What about "I've told her all." ... Doesn't that sound strange?

Also ... according to PONS you can use "all of them" with things but not with people. Even if this is not quite as close to my question, maybe it has some influence.

I've told her all. It does not sound strange at all, and the meaning certainly has not changed. The most I can say is that is sounds slightly more dramatic or emotional.

I have many enemies, and I hate all of them. PONS is an English / foreign language dictionary. Do not rely on bilingual dictionaries for such nuances.

dan.wAlso ... according to PONS you can use "all of them" with things but not with people.

What a strange thing to say. There is no problem at all with using "all of them" with people.