Is it possible to set the iControl Session 'timeout' & 'maximum sessions' through the CLI?

No, there is no configuration file with those settings. The iControl server can receive them from outside (via the methods affecting them) while running, and they affect iControl until it is restarted. They aren't saved, and aren't loaded from anywhere on iControl restart. Just off the top of my head, saving them presents a question because in general mods in iControl are not saved unless you specifically ask to save the configuration, so we avoid bogging down the system saving every time you make a mod. One could imagine saving just a small part of the config if you make a change to this type of setting - that would take more machinery than we currently have. It's not impossible, of course, just would take some design and head scratching to get right.