Almost 2yo regression

My lo is 23 mos and all of a sudden has entered what seems to be a major regression. Typically wakes at 730-8am. Nap 1-3 pm. In crib by 8 asleep by 830pm.

as of 3 days ago he will stand cry and scream in his crib any time we leave his room.(seperation anxiety?!?) We have resorted to sitting in chair and shushing until hes asleep then Leaving. Repeating 2-3x a night. Going to attempt talking thru nanit next. Are we creating bad tendencies by sitting in room? We tried letting him cry