You are right that in order to access the material from which to form a balanced viewpoint you probably need access to a university library (often a question of distance, not permission) or to pay for some journal subscriptions. You are reading books written from a particular viewpoint, and these have often not been through any review process, although some may have (for instance) been submitted to RAE or REF. But if the havn't then you need to take them all with a pinch of salt. Not that they are all nonsense of course. And not all serious historians work in universities. The author of the primary source on the issue of Lord Leitrim, which started all of this, is Fiona Slevin, who as far as I can see does not hold a university position, but whose research seems to adopt academic methodology. So you need to assess the capabilities of the author, unless through a formal review process it has already been done for you