The question becomes: when do you stop looking for vulcan and start thinking of alternative explanations ?
You are on a one-way trip to cranks-ville with this thinking. I'd get that out of your system now. If you think for one second that the cosmology world has not seriously looked at alternative explanations, you're an idiot.
These are just the papers I found that contain the words "alternative", "dark", and "matter" in the title...
We have high-confidence that dark-matter is real. High-confidence does not mean "this is the truth and we cannot possibly be wrong".