Well, if I were you, I'd simply apologize with sincerity for missing Valentine's, and explain that I had a panic attack and wasn't able to make it. Note, sincerely apologizing is not begging forgiveness. Just acknowledge your actions (which I wouldn't be so quick to call a wrong...if you truly had a panic attack, that's nothing you can help), and move on from there.

That's very selfless of you wanting the best for your girlfriend. That's how I've always defined true love (or at least part of it). That being said, with that mentality, I wouldn't consider you to be pathetic to your partner.

I think things will be okay. I think it'd be very strange to schedule a dinner to break up with someone. At least, that's me.

Take care. My best to you.