Studio,
The score you most need to worry about is your middle score. Your low score isn't very good - if you don't have other factors to offset it (large reserves, excellent debt to income ratio etc). Your middle score, however, might be much higher and in the range for prime mortgage loans.
You should find out what that score is and if you can, you need to get your balances to report at ultra low levels on your credit card accounts (and then on only a card or two) to maximize your score before your loan goes through.