Why is the an antenna on top of a water tower?
I can't give you exact numbers, but if you wear a fulls suit of fire protection enchanted armour, you usually don't take much damage. Specifically, if you're on fire, and every second or so you take damage, every other hit you take will do no damage. Same applies to lava, just lava has a faster rate of damage. The higher the fire protection, I assume the higher chances of fire doing no damage.
yeah it is fairly low,but the front wheels are very close at the front corners so the arrival angle is decent. shouldn't be a problem for normal use.