How does Proof of Stake (PoS) improve scalability compared to Proof of Work (PoW)?
In no way. It's a popular myth. It's a wrong question. The correct question is what is "scalability".
What are the environmental advantages of PoS over PoW, particularly in terms of energy consumption?
The same environmental advantages as fiat has over Bitcoin. Fiat currency could printed out of thin air with little to no energy consumption. But when you print fiat and buy goods with it, you indirectly stimulate environmental pollution in various ways.
How does PoS contribute to network security?
It's a wrong question.
Can a malicious attack be carried out under this consensus?
Yes. Any system could be attacked. Check the story of DAO Hack in Ethereum network in 2016 as an example.
What role do validators play in PoS, and how does staking align their incentives with the network’s stability?
They play the same role as parliament in the autocracy. Validators benefit if they keep up with the line determined the ruling party leader and could be slashed if they fall behind.