Sorry to hear your problem.
Mine was blown over in a storm also. I was lucky that I have glass over already. The yak stayed intact.
What kind of strong back is yours?
2X4: wood will twist and bend as moisture changes. The bend you see may spring back (it may not). Imagine you are putting on strips and the 2X4 decides to spring back, you may ended up with a banana. But 2X4 is cheap. I'll buy another one and realign evrything. It is more work but is most reliable.
Plywood or particle board box beam: you are out of luck. The bend is most likely set in. You better off start over and build another one.
If you have to save the material, you have to splint the strong back far beyond the the break and realign all the forms. 3 inches is a lot of twist in the beam. You have to snap a chalk line and use the chalk line as reference instead ( another more permanent option is string between the two ends and spray paint over the line-- this will leave a visiable straight line when the string is removed.) Split the difference between the bent strong back, make it only 1.5 inches in the middle -- 1.5 inches that you have to cut from the center of the forms in order to fit the forms back on to the strong back.
Never trust the strong back again to remain in the same shape as you start stripping. You have to check the straight of your boat from time to time to make sure. These in a long run may be more work than to start over in the beginning.
Good luck with your boat.