Since my miscarriage in January, my body has mostly returned back to normal ish. My body has always been my number one insecurity,

Except she says this. Which means 145 lbs body has been her 'normal'. Deep down she knows she's overweight and not looking or feeling her optimal hence her body has always been her #1 insecurity.

I guaranty that has she been 110 lbs woman, he wouldn't have made that idiotic comment (he thinks he's subtle but he's not).

What these two need is to sit down and have a direct conversation. As direct as possible with no saving of each other's feelings. He needs to help her lose weight as he is a healthy weight and athletic so he knows what works and what doesn't.