>I have a hard time believing that a fusion power source would work at all like a fusion bomb.
No need to. The only thing what matters is the amount of neutrons generated. High intensity flux during 10-30sec. instead of super-high during 0.001ms explosion would do the same damage if the total amount of neutrons generated is the same.
I mentioned Sandia because what they do (more precisely what they did 10 years ago) was the most effective and promising way to get effective fusion - for energy generation as well as to weaponize it without fission part, and i think it is illustrative to look at them to see how progress has stalled (more precisely it was redirected from advancing of the engineering of the fusion into more plasma research) when it became that clear.
I do understand that practical fusion requires neutron flux, but I didn't think we had achieved any significant amount of fusion capable of producing such a flux.
If you have a citation for where Sandia says there are proliferation risks, I would be interested.