The Assertion Query/Request profile, which includes the AuthzDecisionQuery, is not commonly used. We support it but through our SAML low-level API only.
In response to your questions:
1. Yes. For more information, I suggest taking a look at the "Profiles for the OASIS Security Assertion Markup Language (SAML) V2.0" specification.
2. I'm afraid we don't have a specific example of this. I suggest taking a look at our SAML2IdentityProvider example project under the LowLevelAPI folder. The SSOService.aspx page includes a CreateSAMLResponse method that demonstrates constructing a SAML response using the low-level API.
3. You would have to construct the SAML response yourself using the low-level API.
We're happy to assist you getting this working. You're welcome to contact us at [email protected]