Disclaimer: I am not a doctor.
19 years old, around 6'2 and 190 lbs, Are you on medication? Under a doctors care? resting heart rate of 100? "I know it can be inherited" makes me believe you don't know. see a doctor, now.
"successfully avoiding cardio for the past 9 years" Whats successful about that? You would rather "die" than run more than once a week" What? are you serious? Have you ever been anywhere close to being killed? Dude, think about what you just said. There are many forms of cardio besides running. search "predator conditioning"
Walking is absolutely good for you, improving your diet is even better, any small steps you take for general physical fitness is always good.
What are you goals in life? at 19 , that should be crossing your mind, think, realize you probably could not run for your life if your building caught on fire. Don't choose to be weak, don't choose to be prey.
Get a medical exam, then members can advise you on training.