Welcome! Sun conures are wonderful! LOUD but wonderful.
My experience with them has been they can be extremely sweet and cuddly, they love to play, and they can be a bit feisty!
I've found that once I know the different types of squawks from my new birds (scared, upset, excited, demanding) my best way to minimize the demanding squawking is to 100% ignore it. I do a quick check when it's a scared or upset squawk just to make sure they're not hurt and are safe. For the demanding squawks I also often do a quick water/food check to make sure they aren't squawking out of hunger or thirst.
I am sorry for the circumstances which brought your new bird to you but very glad this little one found a new home.