Need help with tire-size related transfer case question

[boynamedsoo]

Went through this about a month ago and have a couple questions for the tech gurus here:
My 2005 4.4 sport needed new tires so ordered new Conti CrossContacts online - from 2 different places, unfortunately. I also moved up a size to 265/50/19 front and 295/45/19 rear. Rears came first, fronts came 3 WEEKS LATE! Mounted rears as I was running on a spare. Here's what happened:
DSC kicked in and reduced power at 80mph and/or when taking curves at 70mph+. I guess cpu freaked out and thought I was losing traction. Then transfer case would howl, but couldn't site a pattern. Also observed an OSV issue with smoking tailpipes after prolonged idle. Coincidental timing but curious if related to tire size difference taxing my transfer case.
Mounted new front tires and no more DSC issues or howling, although very paranoid over EVERY LITTLE NOISE, thinking it may be caused by the bigger tires. Also noticed the gas mileage seems to have gone to sh1t!
Can anyone tell me if I might have damaged anything in my drivetrain from running mismatched diameter tires for those 3 weeks. I drove roughly 6 or 7 hundred miles. Couple dealer techs said should be no problem. I'm kicking myself for changing tire sizes. Sometimes a great deal can bite you in the ass!!
And would my coincidental OSV issue or MPG reduction be related? I'm still blowing white-ish, blue-ish smoke after prolonged idle or stop and go traffic. (gotta love L.A. traffic)
ANY input would be great!! Thanks