To use the correct adjective with the phrase "in detail", think about fewer vs less in number vs amount - but remember "in detail" means specifically or completely already. Examples: I have read your question and answered it "in detail". If you want to read my explanations "in more detail", keep reading. You might find another answer that explains it just as well with fewer details (which ...
When "more" is used before adjective or adverb as "inconvenient" in your example, it is an adverb whose primary function is to modify the following word. However, when it is used before a noun (or sometimes after a noun), it is used as a determiner or adjective. For example: I need more money. More context is required. I need something more (to eat). In the above examples, it means: greater in ...
Hard to say. One would have to know a lot more about 19th century books on usage than I do in order to determine whether "the more" was perceived at the time as being supplanted (and there was an effort to preserve its use). But 'the more' has long been in natural use with the comparative.
You are correct in your understanding more than 2 is > 2, meaning greater than but not including 2 your other phrase two or more is very succinct and clear, you could also use at least 2 to mean ">= 2 ", it does not need to be entirely spelled out as greater than or equal to 2