One of the blades (33", for the small saw) looks like it has up to 40 cracks
in it.

I will get around to testing the twisting theory, hopefully before moving on
to the larger cordless saw.

Seems to me blade tension would be not so difficult to get right, using a
lever (as they do) to release the tension. They probably can provide uniform
tension for a certain small distance of wheel movement when the lever is
restored to operating position. People familiar with spring tension should
know that better than I do.