1/ All of his expectations have fallen through 2/ He fell through with his expectations “He failed to live up to his expectations” is most likely how we would describe this. “Not following through with his own expectations” would work. The idea of falling and expectations doesn’t go unless it’s something like “his expectations fell away” but that is more of a discarding of expectations rather the not meeting them. Alternatively 3/ All of his expectations/plans/dreams have gone to pot This is an old expression that means to lose something to neglect or distraction. Pot in this case is the slang for marijuana the drug and the saying suggesting someone trading their dreams and ambitions for their vice. This would work but it does sound a little dated to me. Additionally, it makes a little more sense to talk about someone else’s expectations/plan/dreams having gone to pot (particular expectations). Example: “my expectations for him have gone to pot”

"Fall through" and "go to pot" are nice idiomatic expressions, but not easy to define. Here's my answer, after some reflection. "Fall through" Only plans and projects, fairly complex things, can fall through, I think. Sentence 2 is certainly wrong because "I" can't fall through. Sentence 1 strikes me as almost fine but not quite. I think "expectations" is too vague and doesn't necessarily carry the connotation of something complex. But in any case it would be better to say his expectations have "been disappointed". "Fall through" is most often used, in my experience, with holiday plans. Your holiday plans might fall through if, for example, the ferry company goes bankrupt and you can't find a suitable alternative. "Go to pot" A subtly different meaning. "Fall through" means to totally collapse so there is nothing left of significance, always (I think) through some outside influence. "Go to pot" simply implies that plans haven't worked out the way we wanted. This may be because of outside influence, or else because the person has made a mess of things. It implies that something could have been done about it, more than "fall through".

No. Only plans and arrangements fall through.