ad 1) Strictly speaking, in unmodded vanilla Main Quest, besides hearing "Alduin" in battles with certain dragons, the first time you hear about him is when you meet Esbern in Ratway. The dialogue is going through
Esbern: "The end is nigh, Alduin returned!" (more or less)
PC: "Alduin... The dragon who's raising the others?" (*)
So it happens earlier than deciphering the wall. And even if it was not clear it is Alduin so far, the player character is not a totally drunken Nord and is able to make an educated guess during conversation.
(*) To adjust for player skipping Kynesgrove quest and not fully aware of dragon raising scheme, my mod changes this line to something more well-known,
PC: "Alduin... also known as the World-Eater?"
ad 2) If you look into it, the relevant dialogue with Greybeards starts with
PC: "I need to learn the Shout used to defeat Alduin."
and following this, it is Arngeir who brings up the word "Dragonrend" first.
So, it is enough for the player character to learn that Alduin has been defeated by a certain Shout. Knowing its name is optional.
@MaxusCorven - good catch about Paarthunax and Odahviing!
Although when Civil War negotiations in High Hrothgar do happen, removing Blades participants totally would be an overkill imho (*). Their contribution there is quick and helpful after all. (**)
(*) So since my mod allows doing Blades quests later, I needed to remove all references to Sky Haven Temple and Esbern, if they are not discovered yet, including Esbern himself - simply gave his lines to someone else who can handle Max von Sydow voice. Fultheim could be fun here, but if he's dead you need a backup npc anyway.
(**) Although they bother you about Paarthunax after they tell you the name of Odahviing, Delphine says just "There's one more thing. We know about Paarthurnax.", without revealing then they learned about him from a book found in SkyHaven - so no change to dialogue is needed for Paarthunax quest.
To sum it up - rewriting the entire main-questline entirely could have been fun, but even more fun was to augment it, without removing vanilla content.