1. it is the shocks. the OEM shocks are spongy on Isuzu's. I replaced mine at 55k and have any no issues since (also take a look at your tire-pressure. an extra 5 lbs will help to stiffen it up a little).
2. Clunk, it is the slip joint in the drive shaft. You can clean it up and relube it, but within 6 months it will be back. It isn't doing an damage. I had mine repacked at 40k and now I have ~100k and it clunks ...
3. If you run the AC or defrost it is normal. If you are worried it is antifreeze just watch the over flow tank.
Finally keep an eye on your oil! check it at every fill up or every 500 miles. Isuzu's will magically eat oil (highway driving they eat more).