How to find out a p2pool's node fee/donation setting? I'm mining LTC on a public p2pool node. The owner says there is a fee of 1%.

Is there any way to verify this is true for me as a miner?
Not really, you have to trust that the owner is being truthful. In actuality they could be stealing every bit of work you submit, but I'd like to think that they wouldn't. 

If you don't trust the node, it's up to you to run your own.