First schematics, DC-DC Converter question
The data sheet shows this table and I've highlighted a couple of sections in red: -

As you can see, the only difference between a design that runs from 12 volts and a design that runs at 18 volts is the inductance value. Given that buck regulators are generally fairly flexible in their input voltage range and that your design is NOT pushing the limits on output current demand, I would choose a 10 uH inductor and fully expect it to work across the range of input voltages from 12 volts to 18 volts.

If there is anything else that I did wrong I would like to hear that
too

A whole bunch of things: -

I would strongly suggest that you use a simulator and fully debug the design before even laying out the PCB. This is not really an option because of the potential for shoot-through. I'm going to say this again because, for this type of circuit (a home-spun H bridge), it's really important: -
$$\color{red}{\boxed{\text{It's really important that you do a thorough circuit simulation}}}$$