Okay, lets look at what happened. The judge denied what is thought to be false allegations, the judge denied documents they didn't bring forth at an earlier time, and the judge denied the request for a GAL. Those things are all in your favor. Don't focus on the fact that your witness didn't testify. As someone else said the judge obviously didn't NEED the witness testimony.
As for your 13yo babysitting, if there is no law in your state as to babysitting age (and even if there is it doesn't always apply to siblings) then it's up to you to determine his maturity level. I would not allow my 13 yo daughter to babysit children that young. I couldn't trust her patience level. I could however trust my 11 yo daughter to do it. In the final decision the judge may order you not to leave the 13yo alone with the the younger kids (and he may not) but I highly doubt that you're going to lose custody over it.
When we were together, you said you'd die for me. Now, I think it's time you kept your promise.