Being a combat medic how advanced was his medical knowledge?
Honestly, not all that advanced. The company aidmen were by and large not all that well trained (by modern standards) but did exceptionally well despite that fact.
What he like a present day EMT?
Not really. If you look up the modern day Army's combat lifesaver (CLS) course that is about the closest thing to the company aidman (the proper term for a WWII "combat medic") nowadays. The closest civilian equivalent would be a first responder course with the additional skill of IV insertion added to it (something you never see in civilian practice).
I know the 11th Airborne had the 221st Medical Unit with them, but how did that work?
Just for further reference, you are referring to the 221st Airborne Medical Company. For an idea how the airborne medical companies operated, you can take a look at the most experienced and first one deployed, the 326th. http://www.med-dept.com/unit_histories/ ... med_co.php
This is the unit that the living history group I founded portrays. I have honestly heard nothing about the 221st before so I can't help with specifics as to what they did, where they served, etc.
For a good idea on how wounded were handled "up the chain", I suggest you read: http://www.olive-drab.com/od_medical_treatment_ww2.php
Did he bring the hurt to the 221st?
Normally, the company aidmen would treat the wounded and then they would be evacuated by a litterbearer platoon if one were available. The aidmen generally didn't go with the wounded as often they had more wounded to tend to or were needed to follow their unit forward. To which medical unit the wounded would be taken would depend upon the tactical situation. If the 221st's aid station was closest they might be taken there but if another company or battalion's aid station were closer they would go there. It wasn't a strict "You're part of this unit so you take your wounded to X" operation. There are even documented cases of American aidmen taking their wounded to German medical stations in extreme circumstances and vice versa.