I have a 2007 infiniti m35x. my vdc light is on. what do that mean?

not reading key or immobilizer [security ] circuit failure https://www.engine-codes.com/p1611_infiniti.html

usually its one of the wheel sensors is gone if in canada go to local part source they can scan it for u and tell u which 1 is gone

Its possible you just tripped a code. Take a OBDII scanner and scan for codes. Its possible that if you erase the codes, they wont come back and all will be well. Write down the codes in case and if it comes back look in to them. Maybe abs sensor.

have the rear axlenuts retorqued and noise should go away.other noise under hood not ringing any bells.

VDC OFF light will always be off unless you turn it off (this is for traction control). The slip light should not be on however, unless you are driving in rain/snow and the VDC is activated.

Were you able to use cruise control? I was not able to use it, because I had the VDC & Slip lights on in my 2006 M35X. My Infiniti dealer checked out two faulty parts. The ICC (Intelligent Cruise Control) and the YAW Sensor. These electronic parts don't break often, but when they do, they break your bank to get them fixed. My bill is over $4,000 CAN. I was kind of lucky, the extended warranty pays for it. The service adviser at the dealership said it does not matter where you buy used car nowadays, especial later models, get an extended warranty that covers electronics or enhanced electrical. These electronic parts are very expensive due to the fact that the dealerships do not stock them, and the turnover is slow.
The manufacturer will have to make us pay for it.

The abs sensor may have been damaged when the repair was done.

You have the latest generation of Nissan's 3.5litre motor (just before they released the 3.7litre). Its very high reving and high perf'. Your 3000rpm at 70mph is normal, I have an Acura MDX 2004 with a 3.5litre Honda motor that does about the same, and I have an Infiniti M35x 2007 that is about the same.
You'll know if its straining if the gas mileage is bad. Watch the mileage as a good indicator of drivetrain issues.

We found a local dealer to install a battery for free as long as we bought the battery from them, I think it cost us less than $10.

Ironically I had the "!" inside the "U" come on this morning as well in my 2007 M35x. Oddly this is indicating that you have low tire pressure. I suspect this is happening due to the temperature change. At least for me as I live in New England and it was very cold this morning.