As I remember it Tolkien went through a few different homes in his childhood, some of them aren't there anymore. It would probably take an effort from someone and agreement from the current owner to get a plaque put up.
Read the book as a child but haven't seen any of the films of that one. I don't suppose it kept to the book though. If nothing else the last movie seems to be about a big battle that I'm pretty sure wasn't in there at all.
The Battle of Five Armies is indeed in the book, it's near the very end where the Dwarves are besieged by the Woodland Elves and the Men of Lake Town who want "a fair share" of the treasure hoard as compensation for the damage done to Lake Town by Smaug, the dragon, who was roused from his mountain-lair by the thirteen dwarves and one Hobbit. Unbeknownst to the besiegers, the Dwarves have sent for aid to their kin in the Iron Hills and an army of Dwarves is heading to the Lonely Mountain. The besiegers are suddenly attacked—but by an army of goblins and wolves, not the dwarves. The besieged join forces with their besiegers to fight off the goblins and the dwarven army arrives and joins the fray. Finally, late in the day, after many deaths the Eagles of the Misty Mountains, who had previously helped Thorin and Company in their passage of those mountains, arrive and attack the goblins with whom they are at war, and the battle is won by the alliance of the erstwhile besieged and besiegers.
