Poland wanted an alliance with Germany was but was laughed off at first. Hitler then aggressively pushed for the Danzig. The British took the opportunity and gave the guarantee to Poland. True, Poland took advantage of that, but Germany didn't need to invade Poland. It could've taken Poland out of the British camp with an alliance: It could take Lithuania and would receive Belarus and other west Ukrainian territories after a war with the Soviets.

Germany would take the rest of Ukraine, the Kuban, and the Caucasus. If he had Poland on his side, he'd have a 35-million strong nation with him. Poland could've provided him with 3 million extra soldiers for the war. Instead, in our timeline, it cost him troops and nearly 300,000 German troops had to be wasted occupying Poland.

In any case, if he truly wanted peace, he should not have invaded Poland. Danzig was simply not worth it. The real issue was that Hitler wanted to conquer Russia and gain control of its oil and agricultural resources and attain autarky.