195/50-15 is acceptable but 205/50-15 is better. 175/60-15 is acceptable but 165/60-15 is better. Any of these will work well.
185 60 r 15 could replace them.
Yes, this is an excellent substitute.
If the front tires have enough room to turn without rubbing anywhere,
No, your speedometer will be off and power and fuel mileage will be adversely effected.
Yes, that is a reasonable substitution.
Your best choices are 205 60 r15.
You can but your speedometer will be off. Want to go wider then go with a 195/60-15.
Yes, you can
Yes, this is a good swap and should work quite well.
Can you replace 205/65/R15 with 205/75/R15
yes
As far as I know, the different sizes you can fit are: 185/60 R15, 185/65 R15, 195/55 R15, 195/60 R15, 205/55 R15 and 215/50 R15 on the 6x15 alloys. Chris from DIDCOT TYRE & EXHAUST