I am not exactly sure what services Breeze makes available to you. I am familiar with Communication Services (basically this is exposing TSAPI).
A station device (Communication Manager Station Extension) can only originate one call at a time, unless you place the call on hold, and even then you are limited by the number of call appearances provisioned on that station (max 10).
I suspect you are running into that limitation, but it is not obvious given your 'what am I doing' description.
If you are using a SIP trunk in your application, you don't have to go through the complexity of using stations on communication manager as your originating device, but you will still be limited by the number of members in the trunk group.
I believe you are going to have to register a DMCC station to be used as the originator for each call (or block of 10 calls) you are placing, which means you need a list of station extensions to launch calls from, or use System Management Service to create stations (and remove them when your task completes).