No, you can't: "stress" and "pressure" sometimes mean the same, but they also have secondary meanings. In your example, "stress" means to emphasize or to make most important. This is different from the stress that comes from, e.g., putting a heavy weight upon something (like trucks going over a bridge). To "put pressure on" something means to push it to the limit. Examples: "His boss put pressure on him to finish the report by Friday." "The heavy snowfall is putting pressure on the roof: it may collapse." Again, this is similar to the first meaning of "stress," but you are using the other meaning of "stress" in your example.

No. stress = emphasis

No. In this sentence the word 'stress' cannot be replaced by 'pressure'. Very well explained by Brad. There is a mistake in the sentence also. The spelling of 'then' is wrong. It should be 'than' as you are comparing two things here.