I have a heart pig who, like yours, had to have oxygen etc and is now on a second course of mega-antibiotics for pneumonia. He is now on 10 syringes of medicine a day and, you know what? Despite the worry, the ultra-vigilance, midnight checking etc, I promise you that he's doing really well! Happy, popcorning, eating, stroppy, pooping, drinking and all of that piggy stuff so hold heart lovely, it could all be OK.
The worst bit was trying to get a reliable diagnosis and medication plan, which is where you seem to be. He's doing GREAT on heart meds, antibiotics for the pneumonia, diuretics for the fluid in the chest and two lots of tummy meds to mitigate the antibiotics' side effects. Me? Not so bad.
We're all with you and your babies. Good luck xx