Turtle,
You are making to much of this, use the ZW and use 5-7 Amp Resettable Breakers for your test. In fact I use 10 Amp Breakers to safe guard my layout and have never had a problem, they pop when they need to, and keep my layout safe. If I had to do it again I would keep the 7 Ampers I gave away, instead of the 10's I kept.
Your problem right now with the test, is your transformer is to small.
PCRR/Dave