[ST30-016] - Can You Still Fight, Luffy?! Of Course!! (Starter Deck EX: Luffy & Ace)

Does "Characters with 6000 base power" also include Characters with 5000 base power or less?

No. After gaining +3000 power, you can only draw 1 card if you have both a [Portgas.D.Ace] Character with exactly 6000 base power and a [Monkey.D.Luffy] Character with exactly 6000 base power on your field.