How long does it take an inflamed cornea to heal due to very severe dry eye, ?

No answer. Unfortunately there is no good answer to your question. Every patient is different and every patient has different severities of corneal dryness. People heal at different rates due to their eyedrops, genetics, and other medical problems and environmental conditions. Due to the fact there are so many variables, there is no answer to your question . I'm sorry.
Depends. It really depends on how aggressively it is treated, and how severely dry it is to begin with. If the dry eye cannot be treated successfully, the cornea will continue to be inflamed and you will continue to have symptoms. Dry eyes can sometimes be very challenging to control. Good luck.
It depends. Everyone's cornea is different, but on average it will take a few weeks with the right medications.