I don't know if you'll have any luck finding someone that has worked on one. Most of the service techs I know are less than thrilled about working on LG's major appliances. I'm not sure something like a dehumidifier would have to be sent in to have warranty work done on it. I know your's is out of warranty however if it does have to be sent in to LG then you're not going to have a lot of service companies that work on them.
When I was reading your post, You mentioned that you verified the float is OK. That float activates a switch. Did you check that switch?