But it’s these conflicts between life and death that are the works main themes. They echo an important principle in that we shouldn’t fear or challenge death, or the nature of death. That we can meet it half-way by valuing life and respecting and not harming others.

Is the use of 'that/they' here accurate (complete sentences). As the the that and they clauses are referring directly to what's preceded them.

Or do they require conjunctions/semi colon.