I would say that ITER has no potential to really point the way for fusion energy, it’s an international boondoggle born of Cold War/Post Cold War nuclear politics. As a vehicle for real science and engineering it’s bollocks. The real, slow, incremental research is being done elsewhere. We’re so far from a viable fusion plant rather than a test reactor that it isn’t even funny. So many basic problems (such as what you’ve outlined) remain unsolved even in a laboratory context, never mind the context of a large plant that would need to operate more or less continuously.