You don't know that she has "graduated" from pot smoking to something harder just because she's broke and looks like crap. I would stop gossiping about her to/with others, too. It just makes you look trifling.
You have to straighten yourself out before you stand on the porch of your (rented) glass house throwing rocks at her about smoking pot (I'll slam her soon enough ).
So that's as bad a 2x4 as I'm gonna give you. This morning anyway.
No..."out her to him" doesn't mean file for divorce and I don't know how you even construed that. What it means is make it become known to him that she is playing both sides of the fence sometimes.
The reason she didn't want your help with the prescrip last night is probably because he was there with her or was going to be and she didn't want ya'll crossing paths. As for her comment about dinner...that makes me think he was RIGHT THERE with her and she was putting on a show for him. No more, no less but I'd hold her to it just to teach her a lesson about saying what she means and meaning what she says.
On another subject that is likely to hit a nerve:
How old are your children?
And please tell me why, if she smokes pot and is shacked up half the time with another pothead, do you find it acceptable to give your child (or children) to her to care for for a week at a time when they would so clearly be better of with you full time?
She can get visitation. One night a week (supervised since she's a pothead) and every other weekend (or whatever variation works for you)
Take back your power.
She has you by the balls and she's the one screwing around.
I'm not telling you to become a jerk.
I'm telling you to put on your big boy pants and be a man.