> 2. It's a fast reactor so lots of high energy neutrons that will cause faster material degradation, higher maintenance cost, more downtime - the economics for fast reactors have never worked (not even in Russia or China), and this is probably why fusion reactors will never be economical (32x greater neutronicity).

Commonwealth Fusion Systems's ARC has an interesting approach to handling this -- using a liquid blanket which can be circulated. Of course, ARC isn't built yet! But if that approach is workable, perhaps it can be applied more generally?