Absolutely not as you are going in the wrong direction. This would be a horrible substitute. The 235 tire would be 11.7% smaller in overall diameter. Your speedometer would read 68 mph at a true 60 mph. Handling, braking, ride, and fuel mileage would suffer. If you wish to switch to a 65 series tire then you will have to go with a 275/65-15. But I highly recommend you do not go with a 65 series tire from a 75 series. I recommend you go with a 70 series tire in the size 255/70-15 which will work well.
no
Yes, that is a pretty good substitute.
Yes, they can
Yes, they can
Yes, you can
You can substitute these tries if need be. But if you do this your car will be off balance.
Normally. yes.
Yes, this is an excellent substitute.
Yes, that is a reasonable substitution.
Yes, you can
no there is too much height difference
It is an acceptable substitute, but know that your speedometer will read 58.7 at a true 60 mph.