AMS connections are pleasant and efficient--much, much better than JFK. CDG, however, is not so good, although if you're in biz, the AF flights within Europe are better than KLM (better food and center seats blocked off, but not the same decent wine in small bottles, although AF apparently doesn't serve any alcohol before about 1 pm).

Your original flight was a 757, right? I'd try for a 330 on the re-routing with good AVOD even in coach. It's a matter of personal preference, but I like the longer TATL routes better, so I would avoid an East Coast connection if possible. If you do TXL-AMS-DTW/MSP, you get nice planes and nice airports for international arrivals (no terminal change!), but the flight to AUS is likely to be an RJ, albeit one of the very nice new larger ones with FC.

You need to figure out what you want and then call DL pretty soon to get your new reservations. There should not be a charge for this, although if you find that your new flights would be cheaper, you should request a refund of the difference.