Prepared this the other day but got busy and forgot it.
1.You asked what type of unit. I defined the above and corrected Turner's misinformation.
2. A "battery" in the artillery is the equivalent-size unit of a "company" in the other branches.
3. Based on your info, he was trained as an antiaircraft gunner and probably served with an antiaircraft battalion but not necessarily the 951st (there were over 700 such units active during the war). All that's certain is he was assigned to the 951st when he was discharged.
4. He may have exaggerated or you may have misunderstood. 300 of 330 is a 90+% casualty rate; incredibly high for a line outfit, much less a support unit.
5. I don't share sources (see below). I have a private library and a network of contacts. If I can handle your question with sources at hand it's "on the house". If not, I charge a fee based on my costs.
I don't share sources that I still use (for a while, Turner bugged me for sources but I had him pegged for a "big mouth" and it turned out I was right). I once made the mistake of sharing a source with the stereotypical "sweet little old lady". She turned out to be a "big mouth" - one of those characters intent on "helping everybody" - a regular "Deep Throat". In no time, my source was inundated with inquiries from what seemed to be every member of every historical and geneological society, quilting club and Wednesday Afternoon Ladies Consortium in this hemisphere. My contact quit me and, when I needed info, I had to "stand in line" with everyone else until I could "recruit" a replacement.
Re Turner. I've been "being nice" for some time now. I've received at least a couple hundred messages to date complaining that his info is confusing, wrong or both (I have no idea why they complain to ME). Half complain THEY don't know what he's talking about and the other half complain HE doesn't know what he's talking about - and they're all correct! His "reference files" consist of a couple long out-of-print books that he shoplifted from Goodwill or some such and most or all of his "research" is simply copied verbatim - he doesn't himself understand what most of it means.