Translation:He was poor but almost never complained.
Byl = he was. Bylo = it was. Byl chudý = he was poor, bylo chudé = it was poor, byla chudá = she was poor.
I am a learner, too, so my reply is not authoritative. I did a quick check for "official" English translations of "chudý" and all referred to not having enough money. See https://glosbe.com/cs/en/chud%C3%BD.
So... I'd say that "IT was poor" wouldn't work, since "it" would not be likely to have money at all. But maybe a moderator can give you a better answer.
"IT was poor" does not make any sense. IT is a word for a thing or animal. In this sentence, we are talking about masculine...
Yes, but in English, we can say something like "the service was poor". In this case, the full sentence could mean something like "the service (it) was poor, but he almost never complained", unless, like BoneheadBass suggested, the word "chudý" refers exclusively to people.
This is an interesting angle. However, it now occurs to me that it cannot be "IT was poor," because the verb is "byl," not "bylo." Well, duh. But on the bright side, we may have learned something about "chudý."