Yes and yes and yes (but not as many graces as you would if you weren’t in a state of sin). Wearing it is still valid. Just see a confessor ASAP so you can get absolved from your sins.
If you want to think about it in a super natural way, you wearing the scapular will keep you safe from temporal harm so you can see a confessor and get your sins absolved.
In the state of mortal sin no supernatural merit (no Divine reward for the practice of virtue) is received. Mortal sin puts an obstacle in the way preventing the effect of previous merit from being realized. If there is final penitence (a state of sanctifying grace at death) all previous merits (which were granted from the times one was in the state of sanctifying grace) are present.
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