I would NOT go to 1000 miles before doing the second 90 degrees. Go out there, take off the valve cover and do it NOW!

Those are stretch bolts. They are designed for this and if you do not stretch them enough, once the engine starts heat cycling you will not have enough clamping force to keep things in place.

I know how you feel about this. It feels like you're going to break something in two pieces when tugging on those bolts, but it must be done that way unless you enjoyed the job so much that you are anxious to do it again.

Good luck,
PS. Congrats on a job well done. LB