Glad you're almost back.
ATROPHY. When you splint anything for 6 weeks, it will take twice as long to recover, and fully heal in quad that time. That is normal.
I was in a hip cast for 5 months, then a short leg cast for 7 months after that. I rode my BSA500MX on the beach at least 15 days with the short cast on
Day I got out of my short cast, after a walker for 2 months, my calf was smaller than my forearms, weaker too. That left thigh was close to the size of my bicepts.
5 days out, I went surfing at OceanBeachSanFrancisco on a 6' hollow day. My surfing buds couldn't catch any waves (they'd been surfing maybe 4 years), I got two, didn't stand on on the first and rode the second to shore. Surfer maybe 25 out of the next 30 days, crutching to the shore, then grabbing my board from my bud's who carried it down to the shore.
You gotta do what you gotta do. Took longer than 4 years to be able to run on the soft sand beach.