Since you're already pushing your seat all the way back & using a set back seatpost, there probably really isn't a difference between the bikes in regards to seat angle... your setback seatpost & seat being pushed back is probably increasing the effective toptube of your current bike... you may not need the setback seatpost on the cervelo and then possibly you'd want a longer stem on the cervelo to even out the top tube.

But I don't know how the differences in heights of the head tube is goign to come into play.

My gut response is that it'll probably fit you and I really generally just prefer seat angles of 73 degrees. I can't get comfortable or my knees in the right spot on a 75 degree seat angle bike.

But I'm gonna caution you that I'm just some random person on the internet who doesn't know a heck of a lot about bike fit other than what I've been through to get my bikes to fit right.

Where are you ordering the cervelo frame through? a bike shop might be able to mock up a dummy/trainer bike to the same specifications as the cervelo frame so that you can try the geometry.