Struggling with Barrel Cactus — would appreciate advice

I want to be honest: I'm not getting great results with Barrel Cactus and I'm not entirely sure why. scarring from cold water splash on the skin has been a recurring problem despite my attempts to address it. I've been focusing on providing the sunniest window or outdoor position available based on everything I've read.

architectural sculptural form that needs no flowers to impress is there in glimpses, which tells me the plant has potential in my conditions. I have it in a south-facing windowsill in full sun which might not be ideal. flowering in late spring to early summer showed some improvement. Two stars for now — not the plant's fault, but not a success yet. I'll update if things improve.