well thats alot of question,
IV is individual value, they boost stats so bigger number is recommended
Eevee is balanced and can become any evolution depend on their stats
atk is physical and sp atk is special, which one better? no, both like 12 and 6 o'clock, usually you have to choose one for each your poke's build
for EV builds, you have to do research, every pokemon have different stats growth and speciality and we cant tell you those hundreds of pokemon unless you do your own research.
that's short explanation, but for deep knowledge you have to read the information on guides by yourself
i would say you have to read guides on forum or googling it
https://pokemonrevolution.net/forum/viewforum.php?f=89