Yarjammer
Wellreadneck
If you can't afford the proper spare and are confident in the sidewalls of the primary four, why not just remove it entirely? Limp back down or out of wherever you are when or if it happens and call in a tow. Personally, I wouldn't run an A/T spare with M/Ts because the tires will handle/react differently. Also two tires of different types or brands with the same P-metric sizing are not going to be the same size. Do a string test to measure the circumference of your spare and compare it to the rest. I'd bet as your tires sit today the spare is .5"-1" smaller due to an initially smaller size and treadwear.