Does using ‘Auto-Attempt’ count towards Open Sesame achievement/trophy

I'm not sure if consuming corpses directly counts. Even if it doesn't, once you've consumed 25, you'll gain the Dine and Dash challenge perk, which allows you to harvest Human Remains, which can be used from your inventory, and are most definitely food.

Ghastly Scavenger is unaffected by Dine and Dash, so if eating corpses directly doesn't count, then I suspect the same would apply for super mutants et al. The easiest way to test this by the way, is to take the perk, and check the challenge counter viewable on your Pip-Boy before eating a corpse.

Apparently you have to load single-player first, and get the very first achievement. After that, achievements will work fine in both single-player and multiplayer.