Two pieces of wood and a bench vise, you can tighten one up or take it apart w/o ever damaging anything. Works with the early oversize ejector rod head too.

As far as keeping it in place,,just tighten it up,the cylinder provides a lot of leverage this way.
It's just a two pieces threaded together. They don't do anything but slide back and forth with hand pressure. Don't over think things by using thread lockers and other stuff on the threads.

If the parts are siezed together a bit too well w/them, you can twist them right apart upon disassembly. Then you really have a problem.