How do openvpn/easy-rsa generated keys map to RSA algorithm variables?

I was reading up a little on openvpn and pki infra and am confused by some of the questions posed by my colleague. :) This answer did help me understand more: http://ift.tt/1FOtvw5

But I am still stuck with some questions. Searching hasn't helped much.

1.1. In the openvpn with pki process, we create the ca first, which gives us the ca.crt and ca.key; more importantly, we get a dh2048.pem and a crl.pem.

1.2. Then we go about creating files (.keys and .crts) for the entities (here, entity means openvpn client or server; basically, a 'client' for the ca)

PKI uses RSA which is as follows (copied from:http://ift.tt/1AabY9j)

2.1 n = pq; p,q = big primes

2.2 phi = (p-1)(q-1)

2.3 e < n, such that gcd(e,d) = 1

2.4 d = e^(-1) mod phi

2.5 (n,d) is the private key

2.6 (n,e) is the public key

I see that the ca.crt is a key, dh2048.pem is a key, client.crt is a text and client.key is again a key. How do these map to the algorithm variables above? Thanks.

EDIT:

An addendum to the question.

The openvpn manual says that both the openvpn server and the openvpn client authenticate each other. I have also read that the CA can be completely offline for security purposes. So, how do they contact the CA if needed? Based on RSA (and since it involves computation) I am assuming that they never contact the CA. Then how does the solution work? Thanks.