Actually spend a week counting your calories eaten and burnt. See how much weight you gain/lose. If you stay steady, eat 500 calories more each day, primarily from protein whilst doing weights exercises. Running won't help you gain weight at all.
Most people that say they can't gain weight don't count their calories, so their results tend to make a lot more sense when they count.
Your base metabolic rate defs wont be 3300, that's what someone that is extremely physically active or extremely heavy (or a combination) would burn.
Foods for high protein include fatty fish, chicken (keep the fat), and caloric dense foods (pasta, pizza, breads, rice, potatoes, fruit juices).
Just make sure you exceed your calorie output everyday and you'll gain weight generally.
Having a fast metabolism is very annoying if you want to get big/gain weight, but it can definitely be done. A lot of people think they eat a lot because they pig out on Pizza on the weekend or something like that, but in reality they simply don't eat enough.
KFC would be fine if it wasn't so high in saturated fats. Enwiabe managed to lose weight whilst eating it multiple times a week (ketogenic diet, KFC is very low carb). Their grilled chicken options are by far one of the best meals on the fast food market for people who hit the gym.