Terms at the time of investment would have been ideal but, if I were in this situation, I'd probably consider the number of unsuccessful investments I had made

Terms at the time of investment would have been ideal but, if I were in this situation, I'd probably consider the number of unsuccessful investments I had made and work to recoup some of those funds. Obviously, you won't want to take so much that it leaves the business in a tight spot. 2x-3x seems fair, since you stated you're an angel investor. I suppose you might convince the company to pay more if you intend to reinvest those funds into one or more angel-type investments.