What is the differance in mending VS recovery spells, spell data looks the same. Heals pet to full in 18 sec.
"Heals to full" is a loose term.
Recovery heals for more than mending. Very simple. Higher level = bigger heal.
Is the heal given by promised mending and promised recovery a static amount for each rank or does the amount healed vary from time to time?
It's static. Your pet is the one casting the actual heal, and unless you give him a healing focus, it will be the same amount each time.