I would also look into hiring a sitter instead of using dad and talk to your attorney about having him pay for it or helping to pay for it. All of that can be included in child support. I would definitely bring up him being left home alone with your attorney as well. Do you have anything in writing where he admitted to leaving your son alone. I hope he said it in an email or text.
Me- BW, 30
Him- fWh, 36
Mostly R'd, minus a few scars...bought a house and got a puppy...And baby makes 3! She arrived August 2013
And as for him, you can't force him to care. Step back, do a BIG 180, maybe he'll realize what he's losing, or maybe you'll find the strength to not care anymore. You deserve someone who puts you and your family as #1. Not someone who can walk away from his son so easily.