Different year, different engine, but your problems are very similar to what I just went through. Cherry pick this reply for any possibilities.
The idle on my Escalade was driving me crazy. Sometimes good, sometimes bad. Sometimes rough when the AC was going, sometimes at start up it was close to stalling. Other times it was just plain rough. Did all the basics.. fuel cleaners, plugs, wires, etc. Then I started doing more expensive things like a new throttle body to rule out the TPS and IAC. It was better, more stable but still shaking a bit.
Then I got a check engine light for a knock sensor. The replacement includes a new intake manifold gasket. I did it myself and noticed how degraded the intake manifold gasket was. I put it back together and instantly noticed the difference. No more shaking no more rough idle. And Ticking noises were gone too. So it was one of the two that solved my problems. And for now on replacing the intake manifold gasket will be one of the first things I do. Because if you do it yourself it's not that expensive