DO NOT ALLOW OVERNIGHT ACCESS.
Please be very careful. I don’t know if he has a record for use of class A drugs, but even if he doesn’t and if someone reports him, you will fall under suspicion, you’ll both be reported to social services, and you’ll have to prove that you have nothing to do with that lifestyle. If he already has a record, this is somewhat moot, but either way, he WILL NOT be granted unsupervised overnight visitation with an infant.
Him leaving is absolutely for the best, before something did happen that could have cost you a SS investigation.
First of all, even if he was law-abiding, judges will not “force” any overnight access for the non-resident parent (him) before the age where WHO recommends you stop breastfeeding, which is age 2. Even then, it’s often argued that a child is much too young to be separated from his or her main caregiver at night time, and that doesn’t happen until age 3 or 4. But this all depends. Still, the “age 2” rule is the norm.
But if you know he uses class A drugs, you need to tell him he has to get a court order if he wants overnights with her, and if he does take you to court, you tell them you want mandated drug testing and you’re willing to submit to them yourself as you have nothing to hide.
If you want to get ahead of this, I would speak to a lawyer about how to report his drug usage in the best way to keep your children safe and away from him.
He doesn’t have a leg to stand on. And remember: he may be panicking not because he wants DD, but because he’s suddenly realized if he doesn’t have her 50/50, he has to pay maintenance. But he’s going to have to for the first few years anyway - he cannot simply take an infant from its mother because he doesn’t want to pay! (Other shit fathers have tried this unfortunately; disappeared for a while and then when CMS rings them, they suddenly want 50/50. Do not be afraid because no judge will simply hand a baby to them.)