Scholars can and regularly do go wrong. Latin knowledge is on the decline, even among people who are supposed to be the best qualified.Regarding the indicas mea issue I should point out that the author of the article really seems to be a careful scholar. https://discovery.dundee.ac.uk/en/persons/martine-van-ittersum Her work with and access to a very important Grotius autograph indicates to me she is an accomplished Latinist. And Grotianais a legit peer-reviewed journal so her paper would most likely have been reviewed by other Latinists. Also, she seems to be very familiar with the historical context of the letter. While I can't intelligently comment on the latin translation, it does seem reasonable to give her the benefit of the doubt as far as her interpretation is concerned.
Indicas meas [historias] would be possible, but again, we need indicas to be a verb in order for the sentence to make sense. Or, as I said earlier, we'd need also to change legisse to legisset.If mea is a substantivized adjective with an implied "things" couldn't mea be agreeing with another noun that is understood from the context? The author suggests indicas meas [historias] which is presumably known by the context. Also, since he may just be saying "my Indian history" it wouldn't seem to require capitalization since it is more of a description than a title (though I have no idea if "Indian" requires capitalization in early modern Latin or not).
All of this speculation seems altogether unnecessary, though, since the sentence makes full and obvious sense as it stands.
The main verb in this sentence is cognovissem. A main verb can be in the subjunctive if it denotes something unreal or potential. For instance, the past unreal, as in "this or that would have been the case", is expressed by the pluperfect subjunctive, like here, cognovissem = "I would have known/realized".What really confuses me about this sentence are all of the verbs. We've got scriberet (imperfect subjunctive) and cognovissem (pluperfect subjunctive), which if I understand subjunctive correctly, it tells me when the action occurs relative to the main verb. I am expecting to find a past tense main verb that these two verbs relate to. But we have an infinitive with legisse and a participle with monente and none of the verbs in the translation suggested are in the forms I expect them to be in.
You need to learn about:How do I go about untangling all of this?
1) reported speech/the accusative-and-infinitive construction
2) ablative absolutes
3) circumstantial cum clauses
4) unreal conditionals
Sorry, but this is a bit much for me to explain in this post. They're concepts that you should easily find explanations about in a grammar or textbook, though. If you plan on reading and/or translating this sort of text, I think you need to acquire some grammar basics, anyway.