If are currently enrolled in a full time PhD, no you cannot register for a second Full Time PhD, you can register only for a second Part-Time PhD.
If you are currently enrolled in a Part Time PhD, yes you can enroll in one more Part Time PhD.
For finding answers to your research deadlock, you need access to research literature. For this you need to request the libraries of those top universities to allow access all their Online Research Journals as guest for some stipulated fee. If you cannot still understand the research content of such literature, find the email addresses of those authors online and email them as to what topics you need to learn so as to understand their research paper. Then you may make some headway. All the best.
And by the way, the question is not stupid. It just happens that one might get interested in doing more than 1 PhD at a time, and I am sure there are more than countable number of such folk who have done so already.
Best
Ramesh C. Bagadi