Great! I'm glad to hear you are seeing better results now.
I would like to reiterate something from before. If you are looking for a safe and well-implemented way of testing your device you should use NI-DAQmx. The MHDDK code is lower-level and offers more opportunities for incorrect configuration and usage. I don't expect that you will actually damage your DAQ board, but if you want ease-of-use and configuration control, I would strongly recommend NI-DAQmx.
It sounds like you might have been pointed to the MHDDK in this thread, when it sounds like all you are asking about is the ability to generate custom data from a simulated device (which you mentioned in this thread).
DAQmx doesn't currently have that capability, but writing your own driver from scratch is really not the way to go.
If you're trying to test your application with a specific set of data, why not just use that data instead of the data read back from the simulated DAQ device?