These ladies are all right ~ go with your gut and get him out of there. Do you have family that will take care of your son for a week or two while you do your interviewing?
As for the question what to say to other providers about why your looking for new care, be honest. You have a gut feeling that things are not right. Mention him being wet at pick up and other concerns that you have. I have one family who met with me and right off the bat told me that their son was a handful ~ when I asked why the parents told me he was not listening and hitting. I told them how I would handle it and through this chat I learned and they learned how we each handle situations. As long as a provider knows that your on the same page as how to correct a behavior then you might just have a fit!
Good luck