I definitely understand your concern.

But now you're talking a different matter from your original post which was slim.

So, has the Ecoli been issue been resolved as well as the other issues? And does it take time to bounce back from these issues?(fully recover)

You are paying money to your vet. Don't leave that office until you have your questions answered.

As far as the RI culture next week being too soon? Considering what your snake has been through, his immune system has probably taken a beating. Your vet is being cautious and wants to be sure that it's gone as well as everything else and that nothing NEW has attacked him.