The Hazon Ish is not clear, and this whole idea of benefit is not clear, because according to this, what’s the difference between a rich person who lived in the city for eleven months and doesn’t participate, and a person who bought an apartment and came for one day? If the whole issue is benefit, the rich person benefits much more than they do.
Second, according to this, why should there be a difference between an individual who fenced himself in, so they can’t get to him, and a Torah scholar who does not require guarding, if the whole basis of the obligation is benefit?
Third, the Tosefta that the Rif brings on page 28a regarding a courtyard in another city, where he has to participate with them in the water channel, is also not clear, since he does not benefit.
Fourth, Tosafot on page 7 [see Kovetz Shiurim, sec. 42] is also unclear.
Fifth, see the Ritva regarding the uncertainty in Rabbi Akiva’s view, and according to this, if the whole issue is benefit, then I don’t care — let’s combine both property and persons together.

I’d be glad if his honor would suggest a different analysis. I was thinking in terms of settlement / rootedness… and according to this everything is clear — and we would obligate the rich man more, because he has more movable property, etc.; he is considered more of a citizen….

I’d also be glad if his honor would explain to us, according to his unique view, why it is impossible to say here that the issue is benefit, even though it seems to me I already said everything, but still…

I don’t see what is unclear. There are halakhic definitions that need to be determined formally. You can’t assess every case separately, so general rules are established. Beyond that, the rich person who lives there only part of the time may be in a situation where he won’t be in the city when they attack, and then he does not necessarily suffer. And it is enough that this is possible in order to establish such a formal rule.
An individual who fenced himself in does need guarding, and he chooses a personal way to protect himself alone (what in Hasidic language is called “a righteous man in a fur coat”). Jewish law does not allow that, because it wants people not to each protect themselves individually, since that is not efficient. Therefore everyone has to be protected together. But Torah scholars do not need guarding at all.
As for the sources you cited, if you have a specific question, bring the sources and ask it explicitly. Unfortunately, I don’t have time to decipher riddle-like writings.