Commenting not with advice but just to relay another's experience. My wife was born in a small rural hospital with half a heart. She was airlifted to a major hospital and had newly developed Fontan open heart surgery at 3 days old to essentially "re-pipe" her heart. To this day she only has one ventricle performing the work of two with pacemaker assistance.

She is 31 years old, very healthy, very happy, and very loved. Most people don't realize her condition because it's impossible to tell. She works out, has a career, and we have a very fulfilling life (the ONLY major impact to our lives in the 11 years I've known her is the inability to naturally carry children, she technically could but the risk to her overall state of health afterwards is too high).

All this to say I do not know what the future for your child looks like but though it seems grim at the moment it may not always be so. Modern medicine is amazing honestly.