This hit home. My father grew up poor and Black in eastern Canada during the depression as the olest boy in a family whiche ventually had 13 kids. There was never enough to eat.
Much like your partner, he'd eat absolutely everything in front of him, regardless of how much it was. He also hoarded food. Like, if Kraft Dinner was on sale for 5 boxes for a dollar (this was the 70s), he'd buy 4 or 5 cases. We were overrun with canned good, boxed foods, frozen dinners, you name it, as if he had to get it while the getting was good.
It's a real trauma. As you know. And my current husband suffers from the same thing. Worst part of his food trauma is his family could afford to buy food, his mother chose not to. Instead she married a deadbeat, starved her own children to pay off HIS back child support all so they could enjoy a military posting to Germany. To this day he has issues. But he's been willing to discuss it.
I'm glad you're patient with your SO. I'm glad you're supportive and understanding and I'm right there with you being angry. Food insecurity messes a kid up in ways many can't even imagine! You've inspired me to maybe write about my dad and my hubby...