I'm not really qualified to answer that but here goes my shot....

Probably the worst advice ever, but I know I'm not the only one thinking this....

Mostly because 15# is a lot of meat, and it is a long time in the danger zone....

I'd slow cook it until it falls apart, mix BBQ sauce into the meat, then cook it some more. Try just a little and save the rest for the next day. If you, or who ever, gets sick you know it's bad. If there are no adverse affects, BBQ only gets better the next day.