My best friend back home went to EMT-B school, then joined the ARMY as a 68W. After talking to him for the first time after he was deployed, he told me they put you through the same EMT class, with a few minor tweaks pertaining to Tactical Combat Casualty Care Provider ie. advanced skills (IV, IO, Needle Decompression, Drugs, Trachs) and stages of care (Care Under Fire, Tactical Field Care, Evacuation Care) necessary for being the sole provider of life support for your unit on the ground.
As far as the combat medic you talked to goes....he is right...combat is totally different...I dont know one civilian EMT-P who has had to deal with a mortar round blowing the legs off of one of his close buddies right in front of his eyes. Yeah, theres training, and cerifications, and comparisons between EMS and TCCC...but all that seems to become besides the point once you're unit is under fire...
Bottom line though....its tough to compare the training of TCCC (or any civilian training) with being an actual combat medic. As my buddy said, and I quote, "You are not a combat medic until you've seen combat." Once you're deployed there are obviously things you see and do that are way out of your scope and training.
To answer your question, instead of continuing all of the talk about certs, I would say take a TCCC Provider course through the NAEMT, if the ARMY wont let you be a 68W, perhaps that course will be your closest bet to understanding how it all works. They will civilian "train" you on the same combat skills. You just wont have the explosions, blood, skull fragments and brain matter of your unit to deal with...