Yes, you had every right to pull your weapon, but... It wasn't the right thing to do. JMHO.
Also, we've all done stunts in our past where years later we all look back and say, I'm surprised I lived this long. The same will happen to you. You'll be amazed how differently you view things in 20 - 25 years.
But dude, you had your g/f with you... not cool to put her safety in jeopardy to have some parking lot fisticuffs.
As it turned out, things weren't what you thought they were going to be. It came damn close to being a killing situation.
And what if he had pulled out a Glock-30 and start busting caps before you even got out of your car instead of pulling a knife? You were pretty startled and surprised he pulled out a knife when you didn't expect it. How would you have responded if bullets started flying before you even had drawn your gun. Tell me that doesn't happen in Florida. How skilled of a gunfighter are you really?