Clearly the ‘go’ in ‘I will go’ does not correspond at all to the Latin infinitive, but to the Latin future tense.
But it does. Your mistake is thinking of will only in terms of a modern usage, instead of its literal and original meaning and etymology. If you look further you may see that will actually corresponds with Latin velle, that does use the infinitive: volo ire “I will (=wish to) go” in the exact same way.
The uses of the infinitive match perfectly, regardless of the future extensions of the word in English.
All I can say to this is that I hope and pray that Essorant does not teach either Latin or English grammar in a school. It may be beside the point whether we say that “like (to) a dog” involves a dative if all you are concerned with is teaching Latin grammar, but it most assuredly is not beside the point if you care about teaching English grammar as well. Teaching that way in a Latin class could cause horrible confusion in the mind of a student with respect to English grammar. I know I would have been horribly confused if my high school Spanish teacher taught that the “broken the bank” in “I have broken the bank” is the object of “have”, and that the “broken” is an adjective that modifies “bank”. I think I would have either shot myself, or the teacher, or both.
What you say is quite true, of course. But nonetheless, native speakers of Modern English are experts in Modern English grammar (as she is spoke) simply by virtue of being native speakers of Modern English, whether they care about formal grammar or not.
I am used to in study of language receiving replies such as
‘there is no connection between one language and another - you
just have to know it’
in roman terms is there any one or two clear cut rules as deciding
when to use the dative with certain adjectives or is it really
too complex for the scope of roman year 1 and 2?
Certain adjectives always take the dative. They simply have to be learned as such. There are some general tendencies – for example, if an adjective can govern another noun other than the one it is modifying, the case of this noun will often be dative or genitive – but there’s no simple way to predict this. Most grammars/textbooks will have a list of adjectives which can take a dative.