-How are these scores in general?
Very good! Your DS has been given a blessing and a responsibility.
-Any suggestions around helping our boy with perfectionistic qualities?
There have been a number of threads about perfectionism, growth/fixed mindset, etc. on the forum. Search for those topics. The author Carol Dweck has also been recommended by a number of posters.
-Are there any others that have experience with their loved one working at a slower pace?
Having a relatively lower WMI, PSI, or both is not unusual among high cognitive individuals. The score alone is not enough for concern, if it's at least average (which this is). Given the clinical observations of your evaluator, it sounds like not something to worry about at the moment. Keep an eye on it, though, mainly from the perspective of perfectionism. Other concerns would depend on the age of the child, and observations of functional impairments (in daily life).
The GAI is clearly your best measure in this situation. Did you have extended scoring? The PRI looks like it would have been warranted.