To answer both questions from Jandrews:
a/r is just my shorthand for "as required". Basically, when the discomfort gets too distracting to function properly or to sleep. 6 weeks post-surgery, this still means once a day or a bit less.
By the way, I was in a sling for between 3 & 4 weeks, but was able to wean myself from it on the early side of what the doctor recommended. PT started while I was still using the sling, but focused on passive range-of-motion stuff for the first few weeks. I was driving with the sling, but my commute is a fairly easy one and my daily driver is an automatic with most of the controls on the left side of the steering column, and I could reach across for the auto trans shifter.
I actually ordered two different seat belt extenders, one rigid (but bendable) and one flexible mesh. I have found them both of value. In my daily driver, because I drive with the seat low, the rigid one is better. In my wife's car, because the seat is much higher, the flexible one is better.
Both were ordered from Amazon, as was my good shoulder ice pack (something else I recommend having for the first several weeks after surgery and also at least for the first week of PT to supplement the icing done at the PT facility.
https://www.amazon.com/Seat-Belt-Lengthening-Accessory-Tongue/dp/B07VF574FP/ref=sr_1_1_sspa?keywords=seat+belt+extender&qid=1566949843&s=gateway&sr=8-1-spons&psc=1&spLa=ZW5jcnlwdGVkUXVhbGlmaWVyPUExUjlLRTQ2NkZUTktTJ mVuY3J5cHRlZElkPUEwNTg2NzE4M1ROTlBCVEJRRlc5RSZlbmN yeXB0ZWRBZElkPUEwNDMyOTg3MzNNODFXMzlWU09DSCZ3aWRnZ XROYW1lPXNwX2F0ZiZhY3Rpb249Y2xpY2tSZWRpcmVjdCZkb05 vdExvZ0NsaWNrPXRydWU=
https://www.amazon.com/Extended-products-Non-Universal-Buckle-Certified/dp/B07VY76WSW/ref=sr_1_5?keywords=seat+belt+extender&qid=1566949890&s=gateway&sr=8-5