it is much more important that you do not EVER get knocked out :D
I've found occasional advanced situations where it's beneficial to get knocked out. Or at least, it makes for a more profitable turn than doing something else. E.g. your units and skills are powerful and available, and you spend most/all your hand cards moving to the space/Crystallizing/etc. I suppose this applies more to the paralysis ability than to knock out, but it's similar. With knock out you'd just need to have a good heal-based setup.
This one seems obvious but I will ask anyway. Lets say the dummy player announces end of round(out of cards). I have an unmodified hand limit of 5 with 1 non-wound card and 4 wound cards in my hand. Can I still take my turn as a standard rest just to get that crystal before end of round? I am going to say yes on this one unless I hear different.
You don't mention but i'm assuming you're getting a crystal because you're on a crystal mine. If so, yeah that works. You could also just do a normal null turn (discard one card) to get the crystal.