I can respond to some of those points. FRCs have been around a long time but Helion isn't just making an FRC, they're making two, slamming them into each other, and then compressing with a magnetic field.

The neutrons from D-D fusion are much lower energy than D-T fusion, and don't cause the same damage to materials. They're similar to fission neutrons, and modern fission reactors last sixty years without refurbishment.

According to Helion and other sources I've seen, their hybrid reaction would only release 6% of its energy as neutron radiation, compared to 80% from D-T. They could also build reactors dedicated to D-D and hence He3 production, designing their power plants to mostly burn D-He3. That would reduce neutron radiation to less than 1% of power output.

Regarding net power and scaling, I'm not competent to talk about it but here's the CEO of Helion going into some detail on their view: https://www.youtube.com/watch?v=G1vyMcqiVtA