Ok well first off, both Apple TV2 and Apple TV3 support 1080. Version 2 supports 1080i where Version 3 supports 1080p. With that said on the box does it say 1080p? Or simply HDMI?
I have and Apple TV 2
Model MD199LL/A
Ver 6.2
720p
From my understanding Seas0nPass has the .ipsw 5.03 firmware which i do see and tried to load. when it gets to the part that says hold the “Menu and Play/Pause” button for 7 seconds it comes back and says "Error Entering DFU mode this device is not supported by Seas0nPass.
Have you tried changing tv resolution under settings/audio&video? There should be an option for 1080p HD.
From what I’ve read there won’t likely ever be a jailbreak for ATV3 unfortunately.