Hello William-
Thanks for your post. And your detailed history.
I want to make sure I understand what information you are looking for....
Are you trying to find a stance that does not cause your hip pain? Or are you looking for a form check on this one? Did you experience hip pain with this set on your light day? Were you using a more traditional stance- (feet shoulder width apart- with a 30 degree toe angle) when you felt the "pop' in your hips?
Form wise: your stance is okay if you are needing to make a modification - as it still enables you to get depth quite easily and you are getting your knees out well. You do seem to be starting the squat by shifting your weight into your toes instead of starting at the top from mid-foot. Is this intentional? It is usually simplest to start the squat with the barbell and lifter in balance over mid-foot.
I would actually like to see your squat from the front 45 degree angle as well- to see your toe angle/knee position from this angle. But in general this squat seems functional for your purposes.
You seem to have enough supination in the right foot- despite your history of tarsal coalition to use this more "frog stance". You said you have FAI in the right hip only? Keep in mind- that not every diagnosis of FAI requires a frog stance squat. You definitely want to let your symptoms be your guide. One thing that I can see in your squat is a lot of movement in the lumbar spine. You actually set your back into hyperextension first at the top and then the backs moves into neutral and then back into hyperextension again. Believe it or not- keeping the back in hyperextension can often cause tendon irritation of the adductor and hip flexor both. I would also focus on maintaining a neutral spine to make sure that this isn't causing some of your hip pain symptoms.
I hope this information is helpful... but maybe I am not answering your question?
Please advise! And good luck.