You have the mass of a proton, but the atomic masses of the others. Atomic masses include the electrons in a bound atom, ie the rest mass of all the electrons minus their binding energy in the ground state.
http://www.wolframalpha.com/input/?i=mass+of+proton++++mass+of+Boron-11+-++3*++mass+of+alpha+-5*electron+mass
Gets closer at 8.68MeV – but still ignores the binding energy of the 5 electrons in atomic Boron-11
The ionisation energies to strip each of the electrons from the boron are: 8.30, 25.15, 37.93, 259.37, and 340.22eV = 670eV = 0.00067MeV (ie an insignificant correction)
