Hmm, I've read the whole thread. I've never owned a GSD, I regularly fuss them in the street (after checking with the owner) and have let my previous dog play with one regularly, including having my dogs head in the GSDs mouth at several points, but it was all in play and gentle. I am aware they are powerful dogs, but I had no idea of the stigma and of the temperament problems with some.
So, having read all the comments and read your posts OP, I would strongly suggest the GSD would not be a good choice for you at this point.
As you've said you'd like suggestions, I would suggest big dogs which are lower maintenance could be:
- Romanian Mioritic Shepherd Dog
- Dogue de Bordeaux
- Spanish Mastin
- English mastiff
There are many other breeds which might suit, but I'm going with the desire for a large dog, lower exercise needs, less needy for constant mental stimulation. I'm not so sure on the DDB for this, but the others are known to be stubborn and wilful at times. They are highly intelligent and pick and choose their moments to listen, but so long as you view this as comical as opposed to anger inducing then it's no major issue.
Many are lead trained with a choke chain or slip due to their strength and can then move to lesser restrictions once they reliably walk well. This would help you with your vulnerability due to your surgery
None of the above would permit a stranger to enter your home if you didn't want them there. They are Livestock Guardian Dogs and are protective of their family and home. The mastins in particular have a style of growl, woof, defend. (Straight to woofing if outside and hear people about). Their woof is so deep and booming they don't tend to need to go beyond this!