Making a dark, suspended chocolate sauce I melted some dark chocolate at a low temperature and added whipping cream to keep it liquid at room temperature. I added more whipping cream after the mixture was at room temperature, but it thickened the mixture, rather than thinning it. It also reduced how dark the chocolate was to a large degree.

I understand the fat in the milk/cream helps to keep the solid chocolate particles in suspension to keep it from settling.

My goal is to make a very dark chocolate sauce at room temperature in which the solid chocolate particles remain suspended, and I would prefer also to not use starches or gums as they change the flavor. I would also like the consistency to be "squirtable," but a maybe a little thicker than Hershey's syrup. I also don't want a sweet sauce.

My questions are these: 1. Why did the sauce thicken instead of thin and 2. What means should I use to achieve the goals of the sauce and 3. If I reduce the fat content of the liquefier by using milk or water, does it reduce the suspension qualities?
1) Well, it happened because you used something that is rich in saturated fat. 

Saturated fat liquefies when heated and solidifies when cool (this is why some places call the type of confectioner's chocolate that doesn't need to go to the fridge to solidify "hydrogenated chocolate", because it is rich in artificially saturated - hydrogenated - fat)

2) My recommendation for you would be adding milk or if you don't want to lose the "darkness" of your sauce, you could add in vegetable oil and food emulsifier (or if you have it on hand, pasteurized egg yolks)

3) You could also change the type of fat you're using, hence the vegetable oil (unsaturated fat) suggestion