3) I am aware of what happens in H-bomb tests. The reaction lasts for a fraction of a second and then all hell breaks loose. Why aren't all of the stars in the sky exploding simultaneously?
This is onyl a problem for FET, not RET.
According to RET the Stars and the Sun are truly massive. This mass creates an attractive force on all the particles. This force is larger than the force of the force caused by the Fusion reactions. This means that the greater force of Gravity overwhelms the force of the fusion explosions and hold the star together.
Now, there is a really good reason that stars don't (usually) blow themselves up. This is because as gravity bulls the gas cloud that forms the star together the fusion reaction will start to occur and create pressure to push the star outwards. However, when this occurs, the force needed to create the fusion reaction weaken and the fusion reaction stops.
This allows the star to one again contract under gravity which in turn increases the force needed to create the fusion reactions and then the fusion reaction starts up again.
It also means that stars are on the edge of bursting, but will not (except in certain circumstances) blow themselves apart. It is a dynamic balance between the pressures needed to cause fusion and the pressures caused by the fusion explosion. However, as the core material of the star is fused into the heavier elements, the pressures need to cause the fusion reaction increases. This means that when fusion does occur it will fuse more material and therefore release more energy.
If a star fuses most of its core's matter into carbon, then the energy released in the fusion process can be enough to blow the outer material off in a massive burst of energy released by the fusion. This is what we call a Nova, or if it is a really big explosion: a Super Nova.