Publishing certificates to inspect SSL connections and browser trusted root cert

Hi All,

I am not very knowledgeable in certificates so any help or advice much appreciated.

We are using a fortigate firewall and would like to use SSL inspection where the firewall intercepts SSL traffic for logging and reporting purposes.

When SSL inspection is turned on at the firewall our users get a security warning which they have top allow in order to proceed.

From the firewall we can download a trusted root certificate that we can push out via a GPO which, when installed, removes the message and correctly inspects the traffic. This is fine for our users on IE however this wont work with Firefox as it uses its own certificate store. Our managed service provider has stated that if we generate a csr from the firewall and sign it using an enterprise CA it will also work with other browsers.

My questions are,

1) Are the certificates...