It doesn't matter how old you are, it matters how tall.
It depends on his height.
Depends on the breed, but normally 14-15hh
For that you would probably need to ride a 13hh pony to 15hh horse.
A hand is defined as 9.8cm so it would be about 15hh.
No.
The average ferel horse in America is somewhat shorter than his domestic cousin. They can be anywhere from 13HH to 15HH on average.
It really depends, a VERY good horse can go for about ten thousand EURO but it can go anywhere up from one thousand. I got a horse a few weeks ago, 5 years old and 15hh tall and it cost me 1 thousand 2 hundred and she was broken. So it really depends
it all depends on your horses size. My newby a 16.2hh TB is underweight so i am feeding him 2kgs of pellets at each feed (morning and night). My other horse- a 15hh appy gets around 1-1.5kg of pellets once a day. :)
For a rider of your height and weight, a horse between 15hh to 16hh would be a good range to consider. A horse around 15.2hh to 15.3hh may be a good starting point and provide a comfortable fit for you. It's also important to consider the horse's build, temperament, and training level in addition to its height.
All martingales are adjustable, and usually available in horse and pony sizes. You didn't mention which type of martingale you would be using. There are standing, running, Irish, German martingales, to name a few, and each has a specific use.
you should barrow your horse
According to the Nokota Registry, the average Nokota horse is slightly larger than the American Mustang, weighing in at about 600 to 800 lbs. and standing between 14hh and 15hh on average.