This is what I think the letter says, but it's my opinion only. ([?] means I wasn't sure enough of the word. Typos, etc. may be mine):
To the person or persons responsible for kidnapping Summer, Not only have you broken Summer's heart and taken her away from her mother and father whom love her very much but you've ruined her chances to become educated [?] her life! You have also broke the hearts of her father, and mother, and brothers and in the midst of all the commotion ruined our lives. You see the public blames us. I don't know if we'll ever find employment again - Nobody will hire my wife and I've been fired from a job I've had for 13 years. We may end up losing everything! When you took our little girl you took our very lives! Why don't you give our little girl back before God's wrath descends on you. You've broken many hearts and [?] especially an innocent 5-year-old girl's heart. One day God will hold you accountable for this crime unless you do something to make this right! Please do the right thing and turn our daughter over to the authorities. We're begging you with all our hearts please do the right thing.
- Summer's father