Good reference is
ChiroGeek's Home Page
You can get answer to many of your questions there.
Bulging discs when actively flared up are usually leaking some disc material. I have had flare ups for years with regard to leaking disc material from disc bulge. This is even after a discectomy at L4 and L5S1. Meaning the discs rebulged after surgery. I have not had fusion surgery or ADR. I think with either of these surgeries the complete disc is removed. While in theory this should mean no more pain from disc it doesn't mean there won't be pain from other sources.
I have had 2 spine surgeries and had 10 years worth of Epidural steroid injections and have taken a low dose opioid pain medicine now 1x/day for 12 years and Toradol injections help greatly to alleviate muscle spasms for me. it helped many people I know with back pain from spasms and most recently my ex has had an acute bout of back pain with spasms so I told him to go to Urgent Care and get an injection of Toradol and it helped him immediately. He still has some discomfort but he couldn't move at all hardly for the pain until he got the shot.
My primary care doc can give this injection, urgent care doctor, ER doctor, Pain Management doctor, etc. It is a Non steroidal anti-inflammatory medication. It may not be given if one is taking oral Nsaids on a daily basis, or one has an allergy to the medication or has problem with his or her kidney function.