I'm really sorry to hear that you've had two major health shocks in one year, let alone in one month. I hope that my experience might help and maybe reassure you.
I had two valves replaced - mitral and aorta - in September and I'm 50. My heart problems started when I had rheumatic fever at the age of 3. It was clear immediately that my heart was damaged but it wasn't until they could do echo scans on hearts (1978 in my case) that the cardiologists could see what the problems were: a calcified aorta and an incompetent mitral valve.
I was expecting surgery in my 60s but everything degenerated quite fast over the past year or so - again, I don't know whether SjS made a difference. The pre-op angiogram showed my arteries in tip-top condition so I don't have the furring problem you mention. However, while one cardiologist was talking me through the echo showing the damage to both valves he said 'and there you can see the typical SjS calcification of the aorta'. That was the first I'd heard of a connection with SjS; I thought the damage was all caused by rheumatic fever.
The surgery was pretty straightforward and recovery better than expected - I have pretty severe SJS-connected neuro issues which complicated everything. I did have a big SjS flare a few days after the operation so make sure your cardiologists are prepared. The anaesthetists knew all about SjS and took good care of my eyes and general hydration.
I'd had surgery before but nothing as major as open heart. In the event, I was pretty calm about it; I knew I had no choice as I'd already gone into heart failure. If I'd known how straightforward it would be I wouldn't have worried much at all. And I'll never be worried about any other surgery. If you'd like to PM me to discuss it further please do. By the way, I'm in the UK and this was all done on the NHS, bless it!
Thinking of you - Chickpea