Applying identity to quantificational notation

I'm supposed to symbolize (Quantificational Notation) and construct a proof for a few arguments which have me stumped.

For instance: -Two is the only even prime number, and no even prime number is greater than three. Therefore, if four is an even prime number, it is equal to two and not greater than three.

I may be doing this entirely wrong, as math and logic are not my forte, but this is as far as I get in writing out the initial statements, before constructing the proof:

1. (N2 • P2 • E2) • (____________) <--- from what I understand about identity, "Exactly" is a combination of "At least and "At most" - I'm not sure how to write an "At most" statement using 2 as I've only ever done it with (x) (y) ( [etc} 2.~(x) Nx• Px • Ex > 3

:. (therefore) N4 • E4 • P4 --> 4=2 • 4 ≯ 3

For 1, after having stated that $2$ is an even prime number, add that 'if anything is an even prime number, then it equals $2$'
For 2, you need to negate an existential, i.e. 'there is not some prime even number greater than $3$'. Also, don't say $Ex>3$ ... now you're mixing up two statements. Instead, use $Ex \cdot x > 3$