it turns out the fusion reaction is more energetic, p + 11B –> 3 He + 8.7 MeV; but for Focus Fusion, i expect the exit beam should consist of around 600 keV particles, or all the exhaust along with some unreacted fuel, in a tightly focused beam, before electrical conversion.

so i get a lower overall velocity in my estimates.
600 keV = 9.61305939 × 10^-14 joule, m[alpha] = 4.0026u = 6.6465 × 10^-27 kg, E = 1/2 mv^2; so velocity of the beam, v = sqrt(2E/m) is about 5.378 x10^6 m/s, or 1.8% of c.

we should keep in mind that fusion yield is not 100% of available fuel, (it might be 20%), and that 80% or more of the exit beam’s kinetic energy needs to be tapped to keep the reactor running for the next pulse, and that the entire process generates a good amount of waste heat to be carried off (up to half of all energy converted).

Even so, rate of fuel consumption is still extremely small. So overall thrust is small.