A lot of that depends on the Cam and who makes it, and what RPM you will turn with it. I had a 480 lift chevrolet cam that only had 350# open rate.
If you know who made the cam, ask them for recommendations. Coil bind is almost impossible with .450 lift unless you have too long of a pushrod or an enormous shim pack to boost spring pressure. Your ticking noise could be many things, but I doubt valve float is the culprit. That ordinarily happens at high RPM where your springs can't push the valve closed in time and they are all open to a degree when they should be seated. Once you've heard valve float, you don't forget it.
1) Single or double springs
Single for a driver with that kind of lift. I would run a beehive spring before I would run a double on a street car.
2) What kind of spring rate should i be looking for and is too much bad?
Again, check with the cam maker. And YES too much spring can be very bad.
3) Will a higher spring rate mean thicker diameter coils? Will this cause coil bind?
Some are thicker but still way below coil bind at 450 lift
Check your rockers for wear
Check your valves for correct lash
Check your studs to see that they are not pulling out of the head
Check for exhaust leaks
Make sure your rockers all move the same amount to rule out a bad lobe
Make sure it's not something in the bottom end.

Make sure all your pushrods are straight
Good luck!