"Some are actors, others make props, and some students are in charge of promoting the play." It's usually easier to read to mix up the language a little unless the repetition is intentional to reinforce a point. I prefer my suggestion above for the flow and variation of language, although your suggestion is also grammatically correct.

* unfamiliar Comma should have space after it, not before.

Can be replaced with “because it will” and it will mean the same thing.

Wholesome food is healthy, and a wholesome person is associated with good health but also good morals. A calm, caring and trustworthy individual.

This must be in the order of ‘otherwise feared’ and refers to what was feared before stimulus measures were announced, in the early stages of the crisis being referred to.

'Chuffed' is more for things which you are extra happy about, like you had a stroke of luck. So as Andrew mentioned, you can be 'chuffed' about a new job, because you might feel lucky to have gotten it. But doing an everyday thing which makes you happy is not something you would say makes you feel chuffed.

They can 'insist on' smoking, or 'persist with' smoking, but not 'persist on'. Certainly breathing in smoke can have it's disadvantages, but a better word there may be 'dangers' or 'risks' (to their health). So you might say "Most of the smokers persist with smoking, even though they know the dangers of it."

'A' is a complete sentence, whereas 'B' is not (or only when given as a short response to a question such as 'Which cat?, as Michael points out). The verb needs to be in continuous form, as a name is given not as a moment in time, but as a continuous thing. Therefore, 'is called' and 'was called' are acceptable, but simply 'called' is not. You would say 'was called' if the cat is deceased or if you are telling a story about a cat that you interacted with in the past but don't anymore (i.e. "the cat which belonged to my first housemate was called 'Tom'"). Alternatively, you may say "The cat called Fatty ..." followed by a verb, in a Subject-Verb(-Object) structure. E.g. The cat called Fatty eats too much.