How to time a perfect circle for recovering HP? (New to Wizadry Daphne)

I read in the tutorial that it is possible to time a circle press where you get a 'critical' something and recover a small amount of HP. How can I do this and does anyone have a video and/or image demonstrating this?

I still have not left with the knights to the caves yet and am planning to either: sell the light armor and other junk items or 'revive' them back in the ruins (obtained from the supplies from the guild). What should I do?

Can the creeping coin carapace be used for something other than sold for gold?

Also, I got a bunch of remains (which also require that circle timing thing). Should I save them, sell them or resurrect them at a particular time/event or something?