I think this may be the final version.
Tier 1: r1 = d1/2 = 6 in (bottom)
Tier 2: r2 = d2/2 = 5.25 in (middle)
Tier 3: r3 = d3/2 = 4.5 in (top)
Height: h = 1.5 in (height of a layer)
V(cake) = pi * ((r1-1/3)^2 + (r2-1/3)^2 + (r3-1/3)^2) * (3*h)
V(frost_side) = pi * (2/3 r1 + 2/3 r2 + 2/3 r3 - 1/3) * (3*h+1/2)
V(frost_top) = pi * (r1^2 + r2^2 + r3^2) * 1/3
V(frost) = V(frost_top) + V(frost_side)
V(jam) = pi * ((r1 - 1/3)^2 + (r2 - 1/3)^2 + (r3 - 1/3)^2) * 1/2
weight = V(cake) * 0.35 + V(frost) * 0.48 + V(jam) * 0.6
cal = weight * 53.4
Remember not to round before the the final answer. Good luck.