Learn English – preposition choice: on; close the gap on

Q1: Is it jealousy of sth or jealousy at sth or jealousy about sth when referring to the reason why someone is jealous?

I would think you would use the same prepositions for jealousy as for jealous.

Paul was jealous of Bill. Paul expressed jealousy of Bill.

Paul was jealous for/over his wife. Paul expressed jealousy for/over his wife.

Paul was jealous for/over Bill's car. Paul expressed jealous for/over Bill's car.

_{Somebody correct me if I'm wrong, but I believe you can use either for or over with jealous in either of the latter two senses it holds above.}

I have never heard that you could be jealous at something or about something, but if the usages are valid, I would expect that you could use them in the same with jealousy.

Q2: Is it common to say jealousy of sb when referring to the person of whom I'm jealous?

Jealousy of/for/over/at/about something is awkward and in my experience little-used. It is more common to say, "I am jealous of him," as in the example first sentences above.

Based on the definition of impression, you'll see that the meaning in this context is a synonym for "the effect", and most definitions recommend the of usage.

It doesn't really make sense to say "the impression about" and whilst you can get an impression from some experience, it depends on the wider context of the sentence.

Given the information provided, I'd suggest you use "the impression of".