what's the distance from ceiling to top of nice looking arch? Put the header behind the arch. That is between the two facings. If that makes sense. You may have to adjust curve of arch when you add 2x's on each side. I do like the look of whatcha got there.
Baring wall? Is that like those folding screens in old Vaudeville doctor's office sketches where the good lookpmg babe goes behind and starts hanging her clothes over? Then it falls over and the doc sez "Helooooo Nurse!"
Measure twice, cut once.
Look at the nail, not the hammer. Watch the fence, not the blade.
If you hook your thumb over your belt you won't hit it with the hammer or leave it layin on the saw table.