Q: Why do most people pronounce the word “forward” (the opposite of “backward”) the same as “foreword” (meaning “preface”)? And why do so many people mix them up and misspell them?
A: Count me among the people who pronounce these two words the same way. In fact, all the dictionaries I’ve checked say the two are pronounced identically in American English. There’s no phonetic difference. Their sounding alike may explain why, as you say, so many people confuse them and their spellings.