John Doe wrote:
... An old friend said that
open end wrenches tend to spread with a lot of torque.

It's never been a problem for me. I've had a HF open-end break, but not
spread. Even if true, your Snappy isn't going to require a lot of
torque. Well, not enough to spread or break even the cheapest wrench.

A cheap set of
Stanley wrenches at the local megastore has a lifetime warranty, but
shipping would be more than the cost of one wrench, sounds like a
silly warrantee.

Indeed it is - same problem with HF warranty. Never mind the warranty,
though - it won't come into play using them on the Snappy.

Is carefully using a vice grip on the threaded nut part of a Snappy
quickchange adapter likely to destroy it? ...

Won't "destroy" it, but might/probably will munge it up. BAD idea, very
poor practice. If you do go that way, don't admit it to anybody.

Bob