why do both verdan and dormon have the accusative ending?
An adjective modifying a direct object would also receive the -n ending.
I give you a lingot!
So to just have a house would be "Mi havas domo"?
No, the direct object always takes an -n, so does the adjective modifying it:
I have a house = Mi havas domon.
I have a big house = Mi havas grandan domon.