Please do not leave your little boy in her care.Ever.
My EXABF and his brother were abandoned by their dad to the care of their alcoholic/addict mom, they both grew up to be addicts. The brother died of an overdose 15 or so years ago.
Get your boy away from her.
My doctor is also my Ex's doctor and he told me "do not leave your daughter alone with him, you never know what could go through his head". And he isn't shooting up, just snorting it.
Among other things my Ex is really good at forgetting doors open (patio doors by the pool) and forgetting knives on coffee table. I've also found a flap of dope on my bedroom floor once, before we moved out.
Go to Alanon. Addicted parents are in no situation to protect their children or even providing basic care for them.