Here are some quick solutions.
Since the IRIS 3.0.0 upgrade, minimum required values for peg-in and peg-out have been halved. Peg-in (BTC) minimum is now 0.005. A transaction with an amount of less than 0.005BTC will cause the loss of that funds. Additionally, you should be estimating to add the miners fees, since the minimum requirements is what the PowPeg should receive.
Read more about the BTC to RBTC conversion here.
PowPeg takes the BTC address from the first input as sender, so you need to convert the private key for that BTC address to get the RSK private key. You can download the tool for the conversion here: https://github.com/rsksmart/utils
Then, with the RSK private key you will be able to access the RSK address with your funds.
Read more about the BTC to RBTC conversion here
VERY IMPORTANT: Check the Federation address every time you want to peg-in.
Here you can find the instructions to check it yourself: https://developers.rsk.co/rsk/rbtc/conversion/networks/mainnet/#btc-to-rbtc-conversion