First of all, welcome to the board.
#1 Idealy yes, the barrel should be far enough back for clearance of the touch hole liner in front of the breech face. FWIW, many seem to prefer a 5/16" liners, however I have always found that the 1/4" liners work quite well.
#2 The fore stock and the muzzle cap do have a subtle flare corresponding to the contour of the barrel. The sides of the wood are not actually parallel, but should be of a uniform thickness (approx 3/32" or so) along the length of the barrel.
Good luck with Chambers kit!
Jeff