Thank you for writing.
I divide and transplant the plants about every 7 years.
Never cut off a stalk.  Pull and twist so that it comes loose from the corm.  Cutting allows infections to enter.  As soon as you pull off a stalk, use a knife to slice off the leaf. 
When ever you see stalks flowering, pull it off. 
From July on leaves and stalks will turn yellow pull these off. 
All material can be composted--it is not poisonous.
Many authorities suggest a light layer of mulch over rhubarb in the winter.  I have never found this necessary after year 2. 
https://extension.umn.edu/vegetables/growing-rhubarb