He-3 is an indirect by-product of the weapons program in the sense that tritium T-3 decays by beta emission to He-3.Regarding the 3He, I'm saying that there are still some small supplies of the material here on Earth, which could be used for a proof-of-concept experiment.
Once you know it works, then it could justify going to the moon or elsewhere to acquire more.
He-3 is pretty expensive stuff since there is not a lot of it. It's a great neutron absorber.
Because tokamaks don't have lot of mass flow.I don't see why a tokamak with a low density of burning plasma inherently has to be heavier than a large chemical combustion rocket.
Chemical rockets have very low Isp (specific impulse), so the thrust comes from high mass flow rate. That's not the case with tokamaks.