web design
DC-DC converters create a lot of ripple and noise.  The capacitor is needed to keep the supply voltage stable for the pot.  Took me a while to figure out what you meant by "loesr", but now I see that's "low ESR". web hosting The best capacitor to use for that purpose is an MLCC cap.  Use a 1uF.  They are small, inexpensive, and have the lowest ESR of any general purpose capacitor.

The capacitor needs to be connected as close as possible to the pot leads, both power and ground which are pins 8 and 4 on the pot in your drawing.  You may or may not have a problem without one,domain registration but it's standard practice to add a .1 to 1uF cap at the power and ground pins for any chip that uses digital logic. 

Cell phone batteries are typically 1C.seo  They are probably the most hazardous batteries you could use to power an atomizer except maybe those 3.2V CR2 Li-Ions, those are horrible too.  They're not designed for the drain currents you would see with an atomizer.  I've seen lots of people talk about using cell phone batteries and even actually attempt it.hosting  If you use a flat LiPo cell, it should be at least 10C and must at least have short circuit protection.  Just use an IMR cell.  Those are the safest ones for our purposes.

Digital inputs from tactile switches typically need to be "debounced".  I don't know about that chip, it may have debouncing already built into the switch inputs, but that's normally something that needs to be considered.renoyadak  Switch contacts make a lot of noise when opening and closing that digital inputs mistake for multiple switch activations.  You usually have the option of debouncing in software or hardware with MCUs, but with that one, you can only hardware debounce.

You can try it as wired in the diagram, but if the pot jumps around on you, that's what's causing it.  Hardware debouncing is usually not a big deal, just a matter of two resistors and a capacitor, but since you are trying to minimize part count and it's already known to work without it, should be okay.  Just bringing up the issue of switch debouncing as a matter of practice.