1- To answer #1. C1, C2 and C3 are on the wrong pins in your drawing.
C3 when on pin 6 is the boost capacitor. It gets charged to almost 2x the logic supply voltage and "floats" on top of the source voltage so that the gate voltage can be 10 volts above the source voltage to turn on the high side FET. A rule of thumb is that it be at least 10x the total gate capacitance of the FET. I would use the .1Ufd. shown in the data sheet even if it is much more.
2-Depends on the current you need. At 180 volts you will probably need to use a ultra-fast recovery diode.
3-Your 180 volt supply should be isolated from the line. So no opto required.
You may have a problem with shoot thru from the high side through the low side. There are drivers that will protect from this or you can "play" with the logic to eliminate it.