Would weighted blankets or sensory toy/fidgets count as a medical expense

Unless they are physician recommended for a specific medical condition (e.g., not for your general health), they would not be deductible.

Does this answer still apply for 2018 TY?

Yes there is no change in the types of things that can be deducted as medical expenses.

I would imagine that a note Rx-ing it for your sleep disorder would be necessary in an audit?