Friend's landlord keeping deposit in PA

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My friend just recently (July 31) moved out of her rented house in PA. The place is basically a dump, falling apart. When she and her two housemates moved in, there was furniture already present (the place was rented unfurnished), left by the previous tenants.

The landlord is now refusing to return the deposit, claiming that the cost of moving out the furniture (which was present when they moved in, and they left when they moved out) exceeds the amount of the deposit ($1550).

First of all, I assume that the landlord, with characteristic incompetence, is not going to send a written itemized list of damages within 30 days, as required by PA state law. (My friend did provide a forwarding address; she did it, as the landlord requested, in a written note left with the keys, so she has no evidence that she did so.) Would it be worth it to just wait in radio silence for the remaining 22 days and try to catch him on the technicality when he doesn't provide written notice? If someone is to write him a demand letter, would it be better in the eyes of the law to do it now, rather than waiting?

In the event that she does have to challenge him on the facts, can he charge her for not removing debris which was present when she moved in? If she does not have photographic evidence that the debris was present, is it likely to be impossible for her to recover the deposit?

Additionally, she had to make a $400 pet deposit, which the landlord has neither returned nor made mention of. She is afraid that if she asks for it she will be told that it's being retained to cover the remaining cost of furniture removal. Does she have anything to lose asking for it? And can he legally withhold it for reasons other than pet damage? (I don't have the lease handy but am trying to obtain a copy.)

Thanks very much.
(I have also posted this to another, similar forum -- I hope that doesn't violate the rules here.)