I am not surprised you feel full at 1200 cals, especially if it is in the form of fruits and vegetables. At first I thought your stomach may have shrunk from your starvation diet days, but then I remembered you are mostly vegan- lol. That is a lot of cellulose and water for the stomach.
It would not be difficult for you to adopt a vegan diet that was more calorically dense, and still have you not feeling too full.
I suggest adding more nuts/nut butter, seeds, bean pastes, coconut, dried fruit as well as ensuring you meet your protein needs. A gradual intake would be best.
I realize that food can be very emotional for some people, and you may be used to this sense of deprivation. It may be scary to try to change. It could very helpful for you to keep track of how you feel when you eat a bit more. Just my two cents.