How likely will I be able to keep my AFSC/MOS if I enlist in the AD Army?

Keep you type job, maybe, just brush up at AIT unlikely. Depending on your assesssmentvyou may need to attend BT as well. Either way you need to acculturate into the Army, very different from the AF. Thank you for your service.

You will need to submit a sister service conversion check through your recruiter. If it comes back favorable then good to go. If not then you will select from what is needed. You will also attend basic again and have your credentials checked to see if you will retain your rank or not.

You MIGHT be able to come into the Army as a Medic but there is no brush up. You would have to go back to BCT as you came from the Air Force and you would go through the Army AIT for Medic as the two services are distinctly different in technique even if some of the training might be the same.

The job would be same but that is about it. Air Force to Army is like Apples to Oranges. And you would find it is no different no matter the service you went to. You would be prior service so would catch some slack in AIT a bit but that is about it.