How to explain the results from different block sizes?
Are these homework questions of some sort?

The hit rate goes up with block size because the first miss in a block essentially "prefetches" the rest of the block, and as long as the other items in the block get used before it is replaced (very common with sequential accesses for both instructions and data), they are automatic "hits" in the cache.

The cycle count goes down because a cache miss takes more cycles than a cache hit.