#2 It does not state Cell can bust a solar-system. It was an english translation error and Also, a Character making the claim he can do it does no evidence make. Meaning; Hyperbole.
#3 Pyron is a being of pure energy. Casually throwing around the same kind of energy is like feeding him snacks. Ki is also not spirit energy, it's life energy. Technically it's all the same thing, but regardless it's what makes up Pyron's essence and why he consumes planets; converts them to energy to maintain his power.
#4 Pyron actually has teleportation and has proven he can travel across interstellar distances at FTL speeds. Since Pyron has no physical body it makes doing any kind of harm to him very tricky. Physically attacking him is all but meaningless.