How familiar are you with the LDAP authentication sequence performed by the Brocade device? Those options you mentioned only have an effect if the authentication sequence includes specific operations.
allow_searches_after_bind option permits the authenticating device to bind once and then perform multiple LDAP directory searches through the Duo proxy without binding again. When that option is not enabled (the default), the Duo proxy expects each LDAP search to be preceded by a new LDAP bind. If your device is not attempting to perform multiple searches with one bind then this would not help.
allow_unlimited_binds option means that the Duo proxy will not require a new LDAP bind to occur in a new LDAP connection after completion of a 2FA request.
Do you know if the Brocade is either trying to perform multiple LDAP searches with one LDAP bind, or if it is trying to perform multiple LDAP binds after 2FA completion in one connection? You can look at the Duo authentication proxy debug output to follow the LDAP sequence. This article describes enabling debug output, and this article is an in-depth guide to interpreting the proxy debug output. You would want to focus on
Or, you could try RADIUS instead as @ikokics suggests. Note that it isn’t possible to pass LDAP attributes (like group membership) back to the device when using Duo RADIUS 2FA with LDAP as primary auth.