There isn't an anti-depressant that helps with the moods and depression but also calms you.
Avanza has a sedative side effect so will help you sleep, but won't calm you like a Bezo will.
That's why your Doctor is trying Seroquel as it's the closest you can come with what you need.
I personally think you may need to be on a number of meds for a while. A depressant with sedation. A bipolar med. And something to calm you.
Unfortunatelyy there is no easy and right answers in this field. It's trial and error. But hang in there. You will get there.
With your mum stealing your meds. Get a lockable steal box, small enough to stash away and hide it. Keep it locked and hide the key.
Maybe even get your husband to drill the bottom of the box to a shelve, so she can't take off with the box.
You need these meds but it sounds like your mum needs them for other reasons. What she did is illegal.