I'd simply just use the eraser tool but with the hardness all the way down and lower the opacity and gently erase a littble bit of the shoulder near the edges
Thats an amazing idea! Athough wouldn't that mean you would constantly have your mouth open? I think theres a way to do it where theyre open by default and when you open your mouth it squints
I'm 15 as well dude, what you could do is contact just a printing service and and get the suit only printed, not sewn. You could go with fabricondemand, I don't know how much it costs but its probably cheaper.