Is it possible to create a disposable address identical to mine?
You have been scammed.

The address with one symbol changed is invalid and all bitcoin cliends reject sending bitcoins to it. So, your partner lies. Tell him to give you a link for his transaction on block-explorer site like blockchain.info


  Now my question, is it possible to create an address similar to mine, but change 1 letter/number?


No. It is not possible.