"I believe...in Jesus Christ, His only Son, Our Lord; who was conceived by the Holy Ghost, born of the Virgin Mary..."
Did God abandon man after Adam fell into sin? God did not abandon man after Adam fell into sin, but promised to send into the world a Savior to free man from his sins and to reopen to him the gates of heaven.
For God so loved the world, that he gave his only-begotten son, that whosoever believes in him may not perish, but may have life everlasting. (John 3:16)
Who is the Savior of all men? The Savior of all men is Jesus Christ.
For there is one God, and one Mediator between God and men, himself man, Christ Jesus, who gave himself a ransom for all, bearing witness in his own time. (I Timothy 2:5-6)
Further reading: CCC 410-412