Advice for negotiating a security deposit?

I moved out of an apartment a few months ago and finally received my security deposit back, however it was quite a bit lower than I was expecting. There were a few charges on there that came as a shock and I'm wondering if anyone has advice on negotiating a higher return. There's two charges specifically that I wanted to negotiate on. One is a pest control fee for flea infestation. As long as I lived in the apartment, we never had a problem with fleas. I've lived in homes with flea infestation before, and it's not something that goes unnoticed. They're a frequent pain, literally. Unfortunately, I have no proof there were no fleas in the apartment, so I'm not sure how to go about arguing this. The second item was a furniture removal fee. Our apartment was empty, so I'm sure it wasn't anything we left behind, but there was a couch and some other junk left in the alley by a previous tenant who had moved out several weeks before. I'm certain the charge was to get rid of the previous tenants junk, but again, I can't prove that it belonged to someone else, so how do I negotiate this?

If it helps, I might have a bit of hand over my landlord. My state law says that a landlord needs to return the security deposit to the tenants 21 days after vacating the apartment. My landlord failed to do this and didn't respond to phone calls I made and messages I left regarding the security deposit until 30 days had passed. Technically, they're supposed to owe the entire security deposit, but getting them to pay up would probably take a trip to court, which I'm not too keen on doing. Still, it's something I may be able to use as a negotiation tool. So can anyone help me out?