Yes, this can be quite a problem when translating.
Your sentence sounds uncomfortable in Gaelic. I think I would try to rephrase the whole sentence, or, in extremis, add another no before the sgòthach meaning 'neither'. Most of the time, we all use language in a fairly casual way, not exactly thinking how the sentence might be construed in a court of law. It is a tradition, particularly in modern English, to give the benefit of the doubt to the strictly logical interpretation. But I suspect this is a development from the Enlightenment, when science and reason were taking over from relying on texts that were not consistent in such matters. I refer to the whole range of texts - scriptures, law, science, philosophy. If you look at really old material you have to keep an open mind on the correct interpretation.
Now since Modern Gaelic has never been used for science, law or philosophy, it means the interpretation of such ambiguous cases has never actually been codified. So basically there is no clear answer. Very unusually, I wrote my Master's dissertation in Gaelic, and I was just careful to avoid any sentence with a complex logical structure like this as there was simply no way to find out what was correct.
Of course all writing is made much more readable by avoiding sentences where there is possible confusion, so my dissertation probably benefited enormously.
It is not at all obvious if you just meet the sentences, without an explanation of what the individual words are doing.
It in fact depends on whether the word is a noun or an adjective. The problem is that the translations in this section cannot always be literal. For example, you may have been told that
Tha an t-usige ann = It is raining
but in fact the literal translation is
There is the water
So we use the tha X ann in a sentence with a noun, to mean 'there is X'. On the other hand, we can use an adjective in
Tha i gaothach = It is windy
We can recognise this construction two ways. One is the i = it, and the other is the typical adjectival ending, -ach which may correspond to various endings in English, but here corresponds to -y.