To answer your questions in turn:
(a) what is the maximum wort temperature at which I can pitch?
100 F. You're going to get some funky esters, though, so be prepared for it.
(b) is there anything risk to waiting a long time after boil to pitch?
If your sanitation is good, no. I have waited over 8 hours to pitch in order to cool down to lager temps. I put my carboy in my fermentation fridge after I had cooled it down to 90 F from boiling. You'll never be sterile, but you can be sanitary.
(c) is it okay to put my primary in the fridge to help it cool faster?
See above. Again, if your sanitation is up to par, no worries. As well, be sure that your fermenter is not open to the air, since refrigerators are crawling with bugs. I'm hoping that you have a yeast starter going? If you're using dry, be sure to rehydrate with water, no matter what the package says. Your goal is to pitch your yeast at a temperature slightly below the temperature at which you plan to ferment. You also want your yeast to get off to a really good start, so they can kill off whatever bugs are in the wort.
No worries! Just don't do something stupid like dump ice into it. Anchor Steam used to cool their wort on their roof, back in the day!