Worker's Compensation and CPP Disability

Hi there, my husband is 40 years old and has been under workers compensation off and on for over 15 years. He has a back injury which has now left him unable to work for several reasons. In June 2017 it was determined by Worker’s that he was not suitable for work and was placed on extended long term earnings until he is 65 (or 67 - eligible for OAS etc.) My question is should he apply for CPP Disability? He was working for the same company for 22 years. We are not sure if money wise if it would be of any benefit to him, the only possibility it would be, would be for the child monthly’s amount our son would receive. I understand that this payments from whscc would be reduced as this would be considered income. not sure how receiving this amount would affect him tax time as well. Would he have to pay back any funds to whscc. Wondering if it’s worth it. Any advise would be greatly appreciated.

Getting CPP-D means his regular CPP will be higher so yes, it is of benefit.
There is tax payable on CPP-D.
If you do get retro, have it paid in the years due so you don’t have a big tax bill.