Allowing interstate insurance sales was intended to deliberately cripple the ability of states to regulate their own insurance markets - the amendments offered by Republicans very specifically exempted any interstate insurance from regulation by the state in which the policyholder lived. This was explicitly designed to create a race to the bottom, where the state with the least restriction on the insurance would become the home of all of the companies involved. So if, say, Delaware declared that insurance companies were immune from lawsuit regardless of their activities, every insurance company would cheerfully move there and the Republican amendment would have ensured that no other state could regular their activities. It was a deliberate poison pill that they knew would destroy the system.
Barring consideration of pre-existing conditions was in the original bill; Republicans had nothing to do with it (other than voting against it).
Even the most draconian tort reform would have a cost savings of less than 0.5%, and that's the optimistic estimate by pro-reform groups who took a serious look at the numbers.
I have good insurance, and I do currently pay a reasonable rate. But guess who had to slog through paperwork and spend hours demanding they pay up when I had to use them recently? Both me and the hospital. And that was for a fairly simple bill. The insurance companies will slow-walk payments, refuse payments, and force litigation - if they pay up at all.