Venting is all good,
I'm at the grandfather stage with a beautiful grand daughter who is so trusting, affable and friendly that fears of your situation enter my mind.
Both of my girls are grown and we managed to get through relatively unscathed, if I could remember how.
I truly wish I could offer comforting sage advice beyond what all the others have expressed, can't but you can certainly add me to the list of folks who feel for you and your family.
The legal system can be exasperating, particularly in dealing with intense cases like yours. All I can suggest is keep a coolness about the situation, stay on track and try not to dwell on the time frame but rather logically gather the facts, assist the investigators and use what time you can to build the case.
Blame and guilt, a hard one to deal with. I'm sure you're aware that no one in your family is to blame. The aggressor is the only one who is and his family will try to protect him. If anything from them hits you in the face, take notes, document any thoughts, keep records and let the folks on your side hear about it. Any prosecutor worth his or her salt will find out things that you have not even considered.
Your baby has been hit hard but as Neo pointed out, kids are resilient. My guess is that somewhere down the line after several flashbacks things will settle down. Only you and yours can figure out how much loving, firmness and anger should be overtly displayed. I suspect that normalcy, impossible as it seems, would be a good anchor point.
Best wishes my man, hang in there.