Indeed crucial parts of your question, slept my attention.
Regarding the fixture substitute you are asking, we need to know the exact model of your fixture in order to be able to help.
Regarding the offline console, here is a short connectivity guide
Once you have loaded Coloursource 40 AV simulator (not the simpler Coloursource 40) and Capture to your computer, you should be able to see sACN Universe 1 in the External universe column of Capture's universe tab. If you see this, it means you have established communication between simulator and Capture. Next step is to create and patch your model to Capture. Same patching information should apply to the simulator as well. After you finish patching both, you should be able to visualise your venue in a live view of Capture with control of your simulator.
In case you can not establish communication, check your simulators network settings (set IP address to 127.0.0.1 in order to enable windows loopback adaptor).
Do not forget that both Capture and Coloursource should have the same fixtures patched to the same channels in order to work properly.