"More likely than not" logically means with a probability greater than 50%. A probability of 50% would be "as likely as not". But the user of the phrase is not making a mathematically precise estimate of probability. They are expressing what they think is likely in an intentionally vague way, and it's misplaced precision to try to assign a number to it. As an opposite, one could simply say ...
"More likely than not" - (1) How likely is it for you in percentage ...
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.
Just FYI, though, "more better" is pretty frequently used ironically these days by the hipsters and the whatnot to simply mean "better". Also, while I think no one would responsibly advocate this use, I think you could make an argument for saying "peaches are more better than apricots than plums are better than pluots".
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 ...
phrase usage - "in more details" or "in detail" - English Language ...