Ok - so, this isn't the court test, like I said - look up Jen Mcintosh for that.
But here is the common man test. My mum had 5 kids, taught primary school for 40 years, never a complaint. Let's pretend she is your mum. Would you leave your kid with that person? I would...
OK, so the kid is ready to spend 24 hours or maybe 18 hours away from mum, true? So my thinking goes like this - if the kid is ready to spend an overnight period away from mum, then it is without a doubt in their best interest to spend a night with dad and a night a week seems ok.
So - some crazy thinking - doctor once told me that babies are not like porcelain dolls. Porcelain dolls are easy to break... Next- you have some maternal concerns, that is natural, but you have not said that your ex is Hannibal Lecter. Just a bloke - yep has some issues - but he would be mad to stuff it all up by leaving the kid so he can go to the pub....
You seem reasonable - you've asked about recommendations, guidelines, etc., so I don't think you're opposed to overnights.Just wanna get some thoughts, etc... My thoughts - why not give it a go?
More random rants: my ex really enjoyed it when the little fella cried when he was coming with me. Actually, she was smug. It will happen, but it didn't take long before the little fella was grasping at me and crying - not so smug then. Realise that it will come with some issues - look for solutions rather than making the issues reasons / justifications for this or that...
So how to help to make it work - offer advice, provide info about food. Do everything you can. Why? Well, it is good parenting, but do it all via email. So if it falls apart, you have evidence that you tried your best. My ex did none of that, but she wanted me to tell her everything, even weighing nappies. She provided me with evidence that she was un-helpful and frankly crazy.
So on that front, back in the day when I still lived with my ex, she went out partying - left me with a 6 month old baby and some expressed milk. I had the idea when the little guy was unsettled and crying. What I did was wrap him in his mum's pyjamas. It helped settle him, but when I asked for something similar after we separated, she tried to use that to prove that I'm crazy...
Just so you know - I'm not crazy.