I mean she was 10 when we first see her but yes, right now, she would be around 11-12 or just a tiny bit older, but definitely not as old as Red (19-early 20s)
I think the important part that Terence is trying to convey is that Scarlet can at least have babies. There’s no point in finding another Wisa woman if she’s unable to have children in regards of reviving their clan
"Give or take" yeah that's alot of take. But it worked Red's entire revenge quest hinges on the fact that he has nothing else to live for. Even if its just to be a companion for Scarlet that probably would have kept him off his vengence. So now he's incredibly shaken.
This is kinda what I mean about redemption can't be decided for oneself cuz Sturges enabled this by keeping them seperate. He wanted to do the right thing and fix his wrongs but he took an important thing away from Red and Scarlet in order to try and clear his guilt. Obv no guarantees how things will play out but clearly a life of peace for Red and Scarlet is still far away.