How to consolidate a large amount of unspent outputs?
To consolidate coins to a single address, just send a transaction for the entire amount stored in your wallet to a new address. You shouldn’t need any outside tools, just use the wallet software to send a transaction to yourself.

You should pretty much never enter your private keys into an online website/service. Access to your private keys could allow that service to steal your coins, there is very seldom a reason you should need to trust someone else to not rob you of your bitcoin.