Why are we (Christians) so willing to let God off the hook when terrible things happen but give Him the credit when things go well? We see bad things happening to godly people all the time and even hear it described as God's will. (Yet, if it were anyone else who desired to see tragedy and suffering befall the innocent or defenseless we'd consider them sadistic psychopaths.)
The atheists are right. It doesn't add up.
One 'simple' but inadequate explanation: God gave us (humankind) free-will and we (Adam and Eve) chose to turn away from Him (sin) so now we live in a fallen (imperfect) world (because that one sin was actually a gateway sin that opened the door for an evil disease to infect all life) and He (being the gentleman He is) doesn't force His will on us so we are left to decide for ourselves if we want the cure.
The cure consists of accepting/following Jesus, the only son of God, who was sent for us to kill as a perfect sacrifice so that the evil curse would be broken. There is a catch however, the curse is only broken for those who worship (the raised-from-the-dead but now invisible) Jesus and acknowledge what his death on the cross represented (a substitute death penalty because we all deserve to die).
But wait, even if we accept the cure we won't be immune to future infections. At least not in this world. Presently the cure can help, but it doesn't take full effect until the World to Come. Someday, probably long after we're dead, God is going to restore His Kingdom and everyone who accepted Jesus' cure will be healed of their sin-infestation forever.
So you see, God has a perfect plan to fix this big mess which is all our own fault to begin with. Get it? And yet I have to ask, if God really has the power to transform this war-torn world into a Kingdom of Paradise then what is He waiting for?
I guess the (typical) Christian response to Epicurus' questions is that God is both willing and able to prevent evil; just not yet and He won't do it for everybody.