The spin luff should be kept pretty tight. A general guide to check the tension is to set the spin and grip the luff in your hand. With proper tension you should only be able to rotate your hand about 90 degrees.

As for the tack line, it should stay put. I've seen people ease the hailyard a few inches in certain conditions but 99.9% of the time the tack and hailyard should remain fixed.

As for the main, you shouldn't need to dump it as far as you are describing. Sailing downwind without the spin and just dumping the main is begging to pitchpole. It might sound scary, but you will be more in control of the boat in heavy winds with the spin up versus keeping it down and dumping the main.