What are the chances of my mirena (levonorgestrel) moving out of place during sexual intercourse or even falling out?

Little chance. Designed to stay in place a long time as a contraceptive, thus should remain in place during intercourse. Supposed to be 99% effective. Pretty good odds. Good luck.
Very unlikely. The iud has been known to move to hide the strings, perforate and move into the belly, and even fall out at times but it is very uncommon. Specifically from sex it would be unusual to say the least.