Disclaimer: this is an answer for why this question is too broad. I am not attempting to actually answer the question because that would be, well, too broad.
In comments, you said:
I think that my question really belongs here and not in cryptography section because it contains nothing about custom techniques and algorithms. The key exchange scheme I ...
For forward secrecy without a synchronous handshake, you want something like the "ratcheting" protocol that Signal uses. It's a quite clever system, really:
Each party generates an asymmetric key pair, and gives the public key to anybody who wants it.
Each party generates and stores some number of [EC]DH parameters - one set for everybody you expect to need ...
Slight addition to the answer provided by @dave_thompson_085.
There is a third encoding format specified in X9.62, that is not replicated in SEC1: hybrid.
It's basically the uncompressed encoding but the first byte encodes the evenness of y just like in compressed format. It's designated by 06 and 07 in the first byte, and they have the same meaning as 02 ...
Your question is:
RSA has n bits of security,
ECC has m bits of security,
We are doing RSA(ECC(...)), how many bits of security does it have.
The answer to this really depends on taking a close look at what RSA(ECC(...)) means and thinking about what an attacker would need to do to break it.
Side note here: elliptic curves don't do encryption -- they do ...