2002 Escalade acting up
 

Hello all. First off, I have a 6.0 AWD 2002 standard size Escalade. After I start up and warm up the truck, I put it in drive and the rpms begin to dip below normal idle and I have a voltage drop for a couple of seconds. After that, I can proceed.
Another problem I have is that on occasion, it stalls on me. Once when I was exiting off the highway. (decelerating) This usually happens when I take my foot off the gas, and begin to apply the brake. As the rpm's drop down, it sometimes stalls out at this point. The truck always starts up immediately.
Last, the "low coolant" lights up when I clearly have enough. Also, on occasion the "security" light comes on while I am driving. If I shut it off, and start it up again, the light goes away. (whoa) what a mouthful.
Please help. Thanks