Thanks for the responses.
I'm comparing my certificate to others, and it looks no different than, say Symantec's root certificate. This certificate is also installed in my Windows certificate store, so Chrome and such have no issues with the resigned certificates. I find that only third-party software that expects a specific certificate (like Google Drive) has issues with this setup. Firefox uses its own store and I have the certificate installed there as well with no issues.
I'm attaching my firewall's CA certificate, as well as the certificate I extracted from Mobileread, in case that gives anyone ideas on how to proceed. (They've both been RARed so they can be attached here...)
_.mobileread.com.rar
Symen (72295).rar