A typical HTTPS RSA certificate is about 3.9kb. ECDSA certificates with ECDSA cross-signed with an RSA root will be around 2.9kb. So this 14kb of HTML response should leave some room for the certificates too.
HTTPS requires an extra couple of round trips (to do the handshake and exchange keys etc). I don't think the whole thing can be optimised to 1 round trip, unfortunately.
It's possible, but not without security implications: