I am suggesting you fill in your worst spots now but again try to only add 1/4 to 1/2 inch at a time, let the bermuda recover then repeat. I would rather see you fill up a hole than scalp the area because of the low spot.
If you treat the majority of the lawn well, it will recover. Bermuda is tough as nails in the turf world.
I am not sure mowing higher is better for the lawn. I know removing more than 1/3 of the blade harms it. If you can not do this with the true cut, then use the rider at it's lowerst setting and mow so you do not remove more than 1/3 of the blade.