Does baby-led weaning develop bad habits like playing with food, not finishing food, throwing food on the ground? My baby has been doing all of these since we've tried the method.

Yes, for the start baby will try to "explore" the food by squeezing and touching the food. You can demo to him, how to put food into mouth. Do not give up, as during initial stage baby is still learning how to self-feed and eat. My boy also threw food on the floor, to test the "cause and effect" when things drop on the floor. I told my boy food is to put in mouth and not for throwing. After sometimes baby will outgrow the throwing stage. Normally baby develop these behaviours it could be due to he/she is not very hungry. You can try to offer food when he/she is not too hungry and in alert mood (i.e. not cranky or sleepy). I put picnic mat under the high chair for easy cleaning. I remember once I gave my baby to try spagetthi the noodle drop all over his legs and feet while he only ate 1 small piece of noodle after the session. After I offered few more times over the week, he slowly mastered it and eat well. It takes a lot of patience and persistent during BLW.