WD40 wont hurt your chain if you dont leave it on there. Use it to clean...ride around the block then lube.
Call WD40...they'll tell you too.
I wouldn't soak it in the stuff but it'll do fine to clean it. But yes, kerosene is recommended.
And I use a block of wood to hold my tank up, when reconnecting fuel lines...otherwise it's gotta come all the way off.