Hi, Derek!
I`m not a teacher, but I`ll try to clear up your doubts. Let´s go:
1. sano, saludable; SANO or SANA (fem.) is HEALTHY. Can be a lifestyle, food or a person. SALUDABLE (both genders) is HEALTHY as well. It is for food, a lifestyle, a habit, not very commonly used for a person.
2. gran, grande; GRAN means GREAT (both genders) is like GRAN PREMIO (GREAT PRIZE), GRAN BARRIGA (BIG BELLY), usually to point out something´s great or large characteristics. GRANDE is strictly BIG. Example: Mi casa es grande. My house is BIG.
3. estacionar, detenarse, aparcar;(They could all mean "to park") ESTACIONAR and APARCAR are TO PARK. Same thing. Usually we use ESTACIONAR in Southern South America and in Spain, whereas up North, as influence of English, they use APARCAR. DETENERSE means TO STOP, although there is a word which is PARAR (TO STOP) meaning the same thing.
4. sustantivo, nombre. (they could both mean "noun") SUBSTANTIVO is NOUN. NOMBRE is NAME. They cannot be interchangeable, do not have the same meaning.
Hopefully I could help you.