Rso,
There is a difference between interpreting a halacha nonliterally and pulling from various sources to demonstrate that ur first impressions of the words are incorrect. For instance it would be wrong to say a king is nonliteral and it means a king of a game of tag or an analogy for a guy who is wealthy. It would however be correct to ask what is meant by the term king as its used and bring a variety of proofs for why the term king isnt comparable to what you might think a king is and show how things even you dont expect to be kingly are considered kings etc.
Ben acher ben is an entirely different question and there are those who say moshiach need not be ben acher ben or even zera shlomo. Famously someone (a lubavitcher?) argued with rav chaim about ben acher ben. The back and forth letters can be found online and rav chaim defended that he need not be!
“the Maharal’s yichus to Dovid Hamelech (according to what I have heard from Lubavichers – they are my only source in this) is through Rashi, who did not have any sons”, the maharals students themselves called the maharal moshiach and the maharal published this.
As for sources type sifrei in hebrew and the R”T kovod kedoshas, then type in yachuf and u will find links quoting the rebbes sichos