The flamethrower is not shorter range. It has the same range, 15, as shotguns and pistols. (The tank flamethrower IS short range.) It is slightly harder to use due to the way the fire arcs, but that's honestly a skill issue.

It's ammo usage is not much faster than the fully upgraded combat shotgun ...

The shotgun is now the preferred method of dealing with small nests, but that in no way makes the flamethrower useless.

For taking out large swarm of biters the flamethrower is still number 1. And the best way to use it is literally to hose the entire area with flames to catch all the biters on ...

Per-save achievements are one of my most wanted features. I do not ever want to delete my steam achievements.

Using a dummy mod and deleting modded achievements works, but it is a bit of a chore.