It is possible to find used 225 45 17 size tires on Ebay or Craigs List. Also check local recycle or junk yards to see if they might have used tires available.
Yes, you can use a 225-45-18 tires instead of 225-50-18 tires.
Doubtful, the 225/65 tires are narrower and shorter.
Yes, they can. They must be mounted as a pair.
Yes, you can mount 225-60r16 tires on a rim made for 215-65r16 tires.
Yes, they are just lower profile tires.
225-60-16 radial tires
On a 2001 Toyota Highlander
Well, isn't that a happy little question? You can put 225 75r15 tires on your Ford Ranger even if the original tires are 225 70r15. It might make your truck sit a bit higher and ride a tad smoother. Just make sure they fit properly and you're good to go!
Subaru Outback
225 70R15
Rotate tires 2 front 225 and 2 back 245
Yes, that is reasonable