Oh hun it sounds like you have been put through the wringer!
My advice is less bf related and more personal, I don't want to offend so please don't take it that way.
Firstly give yourself a break. You are doing EVERYTHING humanly possible to feed your little girl. It's just not happening easily for you, not cos you're not putting your heart and soul into it.
Secondly don't worry about DS he will be fine. NO child has suffered any damage from mum having another bub to focus on and in the long run a sibling is an awesome gift to give to your son.
Lastly and I say this really from the heart - it is OK to bottle feed. I know you don't want to "give up" and I truly understand your pain but sometimes the emotional and physical costs just outweigh the benefits. That is an incredibly personal choice that only you can make.

So have you tried motulum? Could you try just soley bf just for a day? I know C sect does take a while for milk but I would have thought it would be in by now. Also maybe consider some counselling or chat with a trusted friend. This is not an easy thing to go through and you sound like you need some support.

That's all I can say hun. Big Big hugs to you and I hope you gain some peace soon.