[Kube]

You are right about getting different opinions on this one. All-Thread has very little tensile strength and as such will not bend too far without failing.
Being a retired tool & die maker, I would hope I have a better understanding than many in regard to various metals, what they are designed for and when NOT to use them. Yeah, All-Thread has worked for some. However, do you want to be the guy that it doesn't work for?
Do yourself and your family a favor - round up a spring spreader.

The fact that both axle nuts came off with little effort tells me you'd be wise to check those axles very carefully for cracks (developing) before reinstalling them. I'd hate to see you go though all of this work only to have one or both fail in the future.
More often than not, those nuts, not being properly tightened set up the process of axle failure.