The transaction fee isn’t based on the number of cross program invocations or function calls - it’s strictly based on the number of signatures required in the transaction. 1 signature in a transaction = 5000 lamports. The fee is the same no matter how many function calls there are. However, if there are more function calls, then the transaction uses up more compute units, and if it exceeds the default threshold, it will fail. The client is free to specify a higher threshold for compute units on a transaction, but that makes it potentially more costly to a validator, so the transaction is more likely to be dropped or deprioritized. However, the client can add a priority fee to the transaction to increase the chance a validator will process it.
Absolutely. Just get the owner of that address to send the Sol back to you. They’ll even be paying the transaction fee when they do that, so it won’t cost you.