With regard to removing your steering wheel - If its the same as I've seen before it is a tapered shaft and its just stuck on there. There is some play there which is why the bolt moves with the hub when you pull on it.
Soak it down with some penetrating lube and let it sit. If you have a gear puller it might work. That is how I got the original wheel off my '72, which I might add was plastic as well.
If no gear puller then get a buddy and both of you grab the wheel, count to three and give it a jerk, then repeat to cadence simultaneously until it pops off and you both go falling back into the motor well. This works better with a steel wheel though and your plastic wheel will probably break before it pops loose. A gear puller or the like may be your only option.
Another thing to do is one of you pull while the other taps on the bolt with a hammer to try and break the bond on the tapered shaft.
P.S. I cut the plastic steering wheel off the hub to get the puller on there better.
pic of a gear puller and even a pic of one in action on a steering wheel:
Best of luck,
Blue