Dami issues. Let's just prioritize.

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1st, he is in rehab -- they will keep him there coz his mom reported him & he must have tested positive for drug use. You cannot take him out of there to even transfer him to another rehab facility coz legally, you have no right over him -- you are not married. And yes, his mom can sign that you be denied access to him.
36 and still dependent on his mom. This doesn't look good for you.
I hate to be the one to point this out, but: you are alone, really.
Your focus should be on how, without current shelter & financial support -- you & your 2 kids will survive.
Even if his mom is Cruella de buong Filipinas, what can you do?
Hindi mo puede idemanda. (Puede You Tube mo if she comes around to do an Amalyer? episode on you. But that will not advance your interests.)
Ok, she's a devil you say. But you cannot blame her for your sad state now. It is her son, yung ka live-in mo WHO put you in your sad state now. You 2 had 5 years within which he could have helped you 2 become independent of his mom. What did he do? Some men just do not have it in them to be a padre de familia, guiding their family, advancing their family to betterment, taking care of their family, etc.
When he does get around to getting back to you, be prepared, be strong to be the main provider of your family. You have experienced how he can let you down.
5 years is 5 years. You can see it both ways. 5 years you don't want to throw away; so you will continue with this relationship, & be the stronger 1 in charge of your family.
Or, you can look at the 5 years as your quota of trying to make everything work -- and now, it's time to move on.