The momentum is the same, the impulse (and therefore forces) are very different. The bullet is propelled down the barrel gradually - the force is spread through the entire time it takes the bullet to travel the length of the barrel, the reaction forces are applied to the stock gradually, and spread over the area of contact between the shooter and the gun.

A bullet stopped by a vest/plate has a much larger impulse. The bullet needs to be stopped essentially immediately, rather than gradually slowed down over a length equivalent to a rifle barrel, otherwise it kills you. The force is also more concentrated, occuring over the cross-sectional area of the bullet, rather than over the entire contact surface with the rifle.

The issue isn’t forwards, it is down.

You have a tungsten rod held in a clamp on a satellite in a nominally stable orbit. Releasing the clamp just means the tungsten rod is now in essentially the same nominally stable orbit as the satellite.

To deorbit it, you need to meaningfully change its velocity. As tungsten is very dense, that takes a lot of fuel. The more fuel that is used, the sooner the rod will hit the ground and the higher the angle.

Simply dropping it means you have to wait months or years for the orbit to naturally decay, a lot of energy will be lost to atmospheric friction, and there is little control over the impact point. Not exactly what you want in your WMD.

Dropping anything in orbit just means it is still in orbit.

You’d need a lot of fuel to deorbit that cube on a steep trajectory.

It depends on the type of fusion.

The easiest fusion reaction is deuterium/tritium - two isotopes of hydrogen. The vast majority of the energy of that reaction is released as neutrons, which are very difficult to contain and will irradiate the reactor’s containment vessel. The walls of the reactor will degrade, and will eventually need to be replaced and the originals treated as radioactive waste.

Lithium/deuterium fusion releases most of its energy in the form of alpha particles - making it much more practical to harness the energy for electrical generation - and releases something like 80% fewer high energy neutrons – much less radioactive waste. As a trade-off, the conditions required to sustain the reaction are even more extreme and difficult to maintain.

There are many many possible fusion reactions and multiple containment methods - some produce significant radioactive waste and some do not. In terms of energy output, the energy released per reaction event is much higher than in fission, but it is much harder to concentrate reaction events, so overall energy output is much lower until some significant advancement is made on the engineering challenges that have plagued fusion for 70+ years.

But if you could see them, they could see you …

The ideal answer is compost, regenerative agriculture, and (better treated) human-sources waste.

Organic crop yields will almost certainly reduce a bit without animal waste fertilizer, but that is fine since crop consumption will fall by a greater amount due to not needing to feed a bunch of extra animals.