Just get the USB version from their website:http://www.memtest.org/#downiso
If it freezes, it freezes. It's not a big issues. It's such a minimal interface, I wouldn't worry about it. It's pretty straight forward and stable in any version.
Ignore everything else, you are making it over complicated.
If you have any RAM errors, it will start generating errors pretty quickly. You can leave it alone for as long as you want, as long as your system is well cooled. It's just a basic Linux kernel.