This episode is about Walt marking his territory. When Skyler was making that speech saying that Gretchen & Elliot paid for the treatments Walter was ready to explode. He was thinking it was his hard work that paid for the treatments. That's why later when he was drunk he was so angry with Hank and how Jr looks up to him and said "my son, my bottle, my house". In 0106 Hank tells Walt at his school "you got to keep better watch over your turf". The brand of paint at the end is ‘Kilz’ and it’s white paint- meaning he’s killing the White name officially, including his family and the foundation of it. (there is major symbolism in Walt building the trap door to the dirt crawl space himself) Trading it for instead- his Heisenberg identity. The episode is even called Over. As if it officially dies here. "This is the exact MOMENT Walt becomes HEiseNbErG"! Leaving the paint behind at the store. He tries to mask his itch for cooking but he feels fulfilled as Heisenberg, which is obviously alarming- “No deep seated issues there” -Saul. Leaving behind his mundane old life for the rush of living out his Heisenberg Fantasy.